Doser vs kalkawasser vs calcium reactor?
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davidwinn101
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I've done all three over a decade. Dosing is cheap in the front end, although unless you test constantly not really effective at keeping levels constant which is more important per say then the number itself. Calcium reactor is by far the route to go. Some investment required but when dialed in your levels are constant and your tank will thank you for it.
Randy Holmes-Farley
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My Tank Thread
I use limewater (kalkwasser) in my system because it is not an SPS tank and limewater in an ATO keeps it just fine. It's main limitation is that it often cannot keep up in an SPS tank, but folks often still use it with the other methods since it gives a desired pH boost to many systems.
All three methods are good and have their pros and cons. I compare them as well as other methods in the article below"
The Many Methods for Supplementing Calcium and Alkalinity - REEFEDITION
http://www.reefedition.com/the-many-methods-for-supplementing-calcium-and-alkalinity/
from it:
Limewater
Limewater (also known by the German term kalkwasser) has been used very successfully by aquarists for decades, and it is the system that I have used exclusively on my aquarium for 19 years. It is comprised of an aqueous solution of calcium and hydroxide ions that can be made by dissolving either quicklime (calcium oxide, CaO) or lime (calcium hydroxide, Ca(OH)2) in fresh water. The only inherent difference between the two is that if you add a molecule of water to quicklime, you get lime, and that a significant amount of heat can be generated when that happens.
CaO + H2O → Ca(OH)2
Quicklime + Water → Lime
Consequently, dissolving quicklime can make the water quite warm, especially if an excess of solids are added. Most hobby companies sell solid calcium hydroxide as “kalkwasser” or some similar name, although the name technically only applies to the solution.
The calcium ions in the solution obviously supply calcium to the tank, and the hydroxide ions supply alkalinity. Hydroxide (OH–) itself provides alkalinity (both by definition and as measured with an alkalinity test), but corals consume alkalinity as bicarbonate, not hydroxide. Fortunately, when limewater is used in a reef tank, it quickly combines with atmospheric and in- tank carbon dioxide (CO2) and bicarbonate (HCO3–) to form bicarbonate and carbonate (CO3—):
OH– + CO2 → HCO3–
OH– + HCO3– → CO3— + H2O
Once in the aquarium at an acceptable pH, there is no concern that the alkalinity provided by limewater is any different than any other carbonate alkalinity supplement. The hydroxide immediately disappears into the bicarbonate/carbonate system. In other words, the amount of hydroxide present in aquarium water is really only a function of pH (regardless of what has been added), and at any pH below 9, it is an insignificant factor in alkalinity tests (much less than 0.1 dKH). Consequently, the fact that alkalinity is initially supplied as hydroxide is not to be viewed as problematic, except as it impacts pH (see below).
The fact that limewater is very basic (the pH is typically above 12) demands that the limewater be added slowly to an aquarium unless very small additions are made. The reason for slow addition is two-fold: to prevent the local pH in the area of the addition from rising too high (slow addition permits more rapid mixing with tank water to reduce the pH), and to prevent the overall tank pH from rising too high (slow addition allows the tank to pull in CO2 from the atmosphere during the slow addition, mitigating the pH rise). Some aquarists advocate rapid addition, and that is acceptable for additions that would add significantly less than 0.5 dKH of alkalinity to the tank, but an addition of 1.4 dKH (0.5 meq/L; the equivalent of adding 1.2% of the tank volume in saturated limewater or 14 grams of solid calcium hydroxide into a 100-gallon tank) drives the pH of the whole tank too high (up by about 0.6 pH units from where ever it started).
Consequently, limewater is most often added slowly, by dripping or slow pumping. Often it is added as the top off water, replacing most or all of the evaporated water. The pumps add cost and complexity to the system, especially if combined with a float valve or switch (I use the latter and a Reef Filler pump).
As mentioned, limewater has a very high pH. This high pH can have significant advantages with respect to impurities present in the lime. Phosphate and many heavy metals will precipitate, either as calcium salts, or as metal oxides and hydroxides. Copper, for example, may accumulate in some aquaria. Copper hydroxide is very insoluble in limewater because of all of the hydroxide present. From an aquarist’s perspective, there will simply be no copper in clear limewater assuming that it has been given a chance to settle out because copper hydroxide is so very insoluble, regardless of whether there is a copper impurity in the calcium hydroxide solid, or in the source water used. Some aquarists get colored residues in limewater systems, and these colors are coming from metal impurities that did not get into the tank.
Another advantage of limewater may be its ability to reduce the phosphate already in the tank water. While it may be as simple as precipitation of calcium phosphate where the high pH, high calcium limewater meets the aquarium water, the mechanism and extent of this effect in typical reef tanks has not been established.
Another important consideration for limewater is the upper limit to the amount that can be added to an aquarium. The solubility limit of calcium hydroxide in fresh water is about 2 level teaspoons per gallon. If an aquarist has a tank near the high end of calcium and alkalinity demand, then replacing all of the evaporated water with saturated limewater may not be adequate to replace the ongoing losses of calcium and alkalinity. There are a couple of tricks to get a little more from the limewater. These are adding fans to increase evaporation, and adding vinegar to increase the solubility of the lime in the limewater (45 mL of vinegar per gallon of limewater will allow three level teaspoons to dissolve instead of just two). Both of these systems have been successfully employed by many aquarists.
Additionally, the use of a small amount of one of the other balanced additive systems (especially the two/three-part additive systems) in conjunction with limewater is often used by aquarists give a little boost to tanks that need a small amount of extra calcium and alkalinity beyond what limewater can supply, without incurring significant capital costs. Likewise, they can be successfully combined with limewater during periods of low evaporation. Unlike some other supplementation schemes, tank salinity will not increase over time through the use of limewater.
The cost of a limewater system can range from very little to quite a lot. If one uses an inexpensive drip system ($20) and bulk sources of lime the cost can be quite low. Bulk calcium hydroxide available to hobbyists sells for less than $2 per pound (maybe much less in a group buy from a large distributor). The cost per thousand milliequivalents (meq) of alkalinity is on the order of $0.15. I realize that this number means nothing to most aquarists, but I’ll use it to permit cost comparisons of very different supplementation schemes, and at the end of the article, I’ll convert it to yearly costs for some typical tanks. Branded hobby and lab grades of calcium hydroxide will be more expensive. A pound of calcium hydroxide from a well-known hobby company costs about $7, or $0.57 per thousand meq of alkalinity.
Of course, dosing pumps can be several hundred dollars, a good float switch can be $50-100, and one needs to get a reservoir as well (often a plastic container like a trash can; I use 44-gallon Rubbermaid Brute trash cans). Depending on the setup, the limewater reservoir can be far from the tank; even in another room or on another floor of the home. A pump like a Reef Filler or Liter Meter pump can be used to send the limewater significant distances, freeing up space around the tank.
Some people use reactors to deliver limewater. These systems automate the delivery of limewater to the tank, and, of course, the costs rise. They consist of a chamber where fresh water enters, is mixed with solid lime, and the fluid limewater exits the system and travels to the tank. They do not permit any additional calcium or alkalinity to be delivered to a tank compared to other limewater delivery methods (assuming that both use saturated limewater), but many claim them to be less hassle than delivery from a still reservoir. Addition of limewater with the simplest drippers may require daily attention, while delivery from a large reservoir may require attention only once every 1-5 weeks, which is about the same as typical limewater reactors. All of the other comments about limewater apply equally well when used with a reactor, a dripper, or a slow pump from a still reservoir (except that the vinegar/limewater combination is technically difficult to use with a limewater reactor).
On the negative side, limewater does have some concerns that don’t apply to most other systems. One is the effect of overdosing. All calcium and alkalinity additives, if added in sufficient overdose, can case abiotic precipitation of calcium carbonate in the tank. Limewater, however, is especially prone to this effect for two reasons. If overdosed, the high pH of the limewater will rapidly convert much of the bicarbonate in the tank to carbonate, increasing the likelihood of precipitating calcium carbonate. Also, addition of solid lime particles can cause local extreme spikes in pH and calcium that nucleate precipitation of calcium carbonate. Consequently, a limewater overdose, and especially the dosing of lime solids, is by far the most frequent cause of “snowstorm” events where calcium carbonate precipitates all through the water column. In some cases, the tank can look like milk. The good news is that this event usually causes no lasting harm to tank inhabitants unless the amount overdosed is exceptionally large, but it is nearly always upsetting to the aquarist. I’ve had it happen numerous times without losing anything.
Another drawback to systems where the limewater dose is tied to evaporation is that the evaporation may change daily or seasonally. I’ve not found that to be problematic in my system, but others who are more concerned about maintaining a very specific alkalinity may have more trouble with this issue. Dosing limewater on a timed pump rather than to match evaporation may eliminate the concern, as long as it doesn’t exceed evaporation rates.
One final note on lime: The high pH of the liquid and the dust hazard of the solid are not to be treated lightly. Inhalation of the dust is to be avoided. Splashing of limewater onto skin is also to be avoided, and should be followed by extensive rinsing with tap water if it happens. Splashing of limewater into the eyes is especially to be avoided, and the use of safety goggles when using large amounts or in situations where exposure is likely is prudent. Extensive and immediate rinsing with tap water, followed by professional help would be advised in the case of eye exposure.
Calcium Carbonate/Carbon Dioxide Reactors
Calcium carbonate/carbon dioxide reactors work by removing water from the tank, adding carbon dioxide to reduce the pH to about pH 6.5, and then allowing the more acidic water to dissolve solid calcium carbonate media that is present in a mixing chamber. The water is then returned to the tank with its extra calcium and alkalinity (bicarbonate):
CaCO3 + H+ → Ca2+ + HCO3–
Reef tanks employing such reactors typically run at a pH below that of natural seawater, with typical tank pH values of 7.7 to 8.1. The reason for the low pH is the constant delivery of low pH solution to the tank, adding both excess CO2 and bicarbonate. There is no way around this completely, but some reactors incorporate a second chamber, allowing the liquid to pass over additional calcium carbonate media, making better use of the carbon dioxide that is actually added. Aquaria then blow off this extra CO2 and the pH rises, but the effect is typically not complete, and the pH often stays below what would be the case if the same tank water were fully aerated (that is, equilibrated) with normal air.
The media used is important in these systems, with the aragonite form of calcium carbonate being more readily dissolved than the calcite form (although both work). Also, the nature of the impurities can be very important, as nearly all of the impurities will be dissolved and delivered to the tank. Some of these impurities may be desired by the aquarist (such as magnesium and strontium) and some may not be (such as phosphate or copper). Phosphate in reactor media has sometimes become a point of competition between commercial suppliers of media for such reactors, but I would advise aquarists to be skeptical of some of these claims.
One big advantage of these reactors is that they can be scaled to deliver any amount of calcium and alkalinity needed by any tank. For this reason, they are greatly favored by those who have tanks with a high demand for calcium and alkalinity. Because of the low pH that often results, many of these aquarists choose to dose limewater in conjunction with the reactor, not because the reactor cannot supply enough calcium and alkalinity, but purely to raise the pH in the tank itself. The synergy between limewater and CaCO3/CO2 reactors involves more than just pH. Limewater uses up CO2 and CaCO3/CO2 reactors deliver it to the tank. Together, they combine to keep CO2(and consequently, pH) more in line with natural seawater.
Calcium carbonate/carbon dioxide reactors take up a substantial amount of space, since one needs a carbon dioxide cylinder, a reaction chamber, and a pump. Typically, these systems are used close to a tank, but they could be remote if appropriate water flows to and from the tank could be worked out. Once an aquarist has properly adjusted the reactor system, it requires minimal monitoring for a substantial period. Tank salinity will not increase over time using calcium carbonate/carbon dioxide reactors.
The likelihood of problems from overdosing using such a reactor is minimal. Since the pH is typically low, even substantially elevated calcium and alkalinity values may not cause a dramatic calcium carbonate precipitation event. More likely is just slow precipitation onto heaters and pump impellers. Accidental delivery of large amounts of CO2 to the tank is a concern, but that is a rare accident.
The initial costs of such reactor systems can be considerable, typically about $300-600 for the reactor itself, plus additional costs for the CO2 apparatus. Media costs vary, but a bit over $2 per pounds is typical. That puts the media cost at about $0.30 per thousand meq of alkalinity. DIY ground limestone can be used as media for a tiny fraction of this cost, if you can find it locally. The carbon dioxide cost also needs to be figured in, so that might push the total to about $0.40 per thousand meq of alkalinity.
The primary safety concern for these systems involves the carbon dioxide gas cylinder. Any high-pressure gas cylinder can be very dangerous if the cylinder head should become damaged. So be careful to not drop such cylinders least they become rockets.
Two-part Balanced Additive Systems
There are now a plethora of two-part balanced systems for supplementing calcium and alkalinity, as well as DIY recipes that I have published and for which suppliers sell quality DIY ingredients. These are always liquid additives that you add equally to tanks to supplement both calcium and alkalinity. In the DIY version, magnesium is added to the aquarium as a third solution, although it need not be added especially frequently. The rational for this type of product is that the bicarbonate and carbonate that one might like to dose to supplement alkalinity are not readily compatible with the calcium that is also needed. So one portion contains calcium and the other contains the alkalinity. When a DIY is used, the magnesium sulfate in it is not compatible with either part, so it needs its own solution.
In the simplest form, such a system would be provided by any calcium salt at one concentration in one bottle, and a carbonate alkalinity supplement in the other bottle. Within that constraint, manufacturers have a fair amount of room to play. Typically these additives claim go a step further. When the calcium and alkalinity are taken out of the picture, as they will be by calcification in the tank, then the ions that remain are often described as having the same ratios of ions as natural seawater. Assuming that this is true, then the “residue” is simply more salt for the aquarium. Over long periods of time the salinity will build up due to this process (an effect that is quantified below), but there will be no significant buildup of specific ions in the tank.
In order to accomplish this, manufacturers could use a variety of calcium salts in the calcium portion, for example. They could use calcium chloride, calcium sulfate, calcium bromide, and a variety of other similar salts. They could also put magnesium and strontium in this portion as they would not be compatible with the alkalinity component.
The alkalinity portion of these systems is more complicated. As has been shown in other parts of this article, alkalinity can be provided as bicarbonate, carbonate, or hydroxide. I don’t know of any commercial supplements that use hydroxide for a two part system, but the commercial ones do use bicarbonate, carbonate, and mixtures thereof. Consequently the pH varies substantially between brands, and the various brands of these products should not be thought of as identical for this reason, if no other. In order to attain the natural seawater residue, the alkalinity portion could contain sodium bicarbonate or carbonate, potassium bicarbonate or carbonate, lithium bicarbonate or carbonate, etc.
I’ve not seen any independent test of whether these actually produce a residue equivalent to natural seawater, but I’ve seen no particular reason to doubt it, at least for the major ions. When it comes to the trace elements that might concern some reef keepers, it seems unlikely that these products will be any less prone to having uncontrolled levels of trace compounds like copper than are commercial salt mixes, or any other supplement of calcium and alkalinity, but that remains to be determined (at least as far as I know).
One issue that has confused some reef keepers, however, is the presence of trace elements. Assuming that these products are actually formulated with every ion such that a true natural seawater residue remained (let’s call this the “ideal” product), then it will necessarily contain such ions as copper. Since copper is elevated in some reef tanks, and is toxic to many invertebrates, reef keepers have wrongly criticized this method as adding more copper. That’s actually not what would happen. Since these products leave a natural seawater residue, and since copper may be elevated in concentration in many reef tanks relative to seawater, then using these “ideal” products will actually LOWER copper levels because when the increase in salinity is corrected, the copper will drop.
For example:
You have copper in your aquarium at 4 ppb and salinity of S=35.
You add a two part additive that over the course of a month raises salinity to S=36, and raises copper to 4.02 ppb.
Then you correct the salinity back to S=35 by diluting everything in the tank with fresh water, and you get a final copper concentration of 3.9 ppb.
Does this happen in real products and not “ideal” products? I have no idea. But the statement by manufacturers that it contains all ions in natural ratios, including copper, should not be viewed as a concern that it is exacerbating a heavy metal problem.
The rise in salinity of these products over time can be very roughly calculated, though there are several reasons why this calculation is only an estimate. For every 1000 meq of alkalinity added in this fashion (and the matching amount of calcium) these products will deliver on the order of 60 grams of other ions to the tank. In a tank with a low calcification demand (defined later to be 18.3 thousand meq of alkalinity per year in a 100 gallon tank (0.4 dKH/day)) this effect will raise the salinity by 3 ppt per year (compared to a normal salinity of S ~35). In a high demand tank (defined later to be 219 thousand meq of alkalinity per year in a 100 gallon tank (4.4 dKH/day)), the salinity will rise by 35 ppt in a year, or approximately doubling the salinity. Consequently, the salinity should be monitored closely in using these types of additives, especially in a tank with high calcification rates.
Many people have begun to use dosing pumps to deliver these sorts of additives more uniformly across a day/night period with less work by the aquarist. Such pumps can be obtained starting under $100 for each part dosed this way. There is no need to dose the magnesium part this way, since very little is actually required and once a week is plenty often enough.
The costs of these systems vary a bit. The original B-ionic from ESV costs about $34 for 1 gallon of both parts (10,600 meq of alkalinity), or about $3.20 per thousand meq of alkalinity. It has a pH raising effect, similar to my DIY Recipe 1. The B-ionic Bicarbonate version is more expensive, and is necessarily more dilute than is the original because sodium bicarbonate is much less soluble than is sodium carbonate. If your tank pH gets too high using one of them (such as the original B-ionic), then it is reasonable to switch to one that has a smaller pH raising effect (like the bicarbonate B-ionic or my DIY Recipe 2 using baking soda).
The DIY recipes can be far less expensive, depending on what grade of ingredients you use. Buying ingredients from a place such as Bulk Reef Supply will cost roughly $10 per gallon (total cost of all parts, so 1 gallon calcium, 1 gallon alkalinity, and a few cups of magnesium additive), or about $1.40 per thousand meq of alkalinity.
All three methods are good and have their pros and cons. I compare them as well as other methods in the article below"
The Many Methods for Supplementing Calcium and Alkalinity - REEFEDITION
http://www.reefedition.com/the-many-methods-for-supplementing-calcium-and-alkalinity/
from it:
Limewater
Limewater (also known by the German term kalkwasser) has been used very successfully by aquarists for decades, and it is the system that I have used exclusively on my aquarium for 19 years. It is comprised of an aqueous solution of calcium and hydroxide ions that can be made by dissolving either quicklime (calcium oxide, CaO) or lime (calcium hydroxide, Ca(OH)2) in fresh water. The only inherent difference between the two is that if you add a molecule of water to quicklime, you get lime, and that a significant amount of heat can be generated when that happens.
CaO + H2O → Ca(OH)2
Quicklime + Water → Lime
Consequently, dissolving quicklime can make the water quite warm, especially if an excess of solids are added. Most hobby companies sell solid calcium hydroxide as “kalkwasser” or some similar name, although the name technically only applies to the solution.
The calcium ions in the solution obviously supply calcium to the tank, and the hydroxide ions supply alkalinity. Hydroxide (OH–) itself provides alkalinity (both by definition and as measured with an alkalinity test), but corals consume alkalinity as bicarbonate, not hydroxide. Fortunately, when limewater is used in a reef tank, it quickly combines with atmospheric and in- tank carbon dioxide (CO2) and bicarbonate (HCO3–) to form bicarbonate and carbonate (CO3—):
OH– + CO2 → HCO3–
OH– + HCO3– → CO3— + H2O
Once in the aquarium at an acceptable pH, there is no concern that the alkalinity provided by limewater is any different than any other carbonate alkalinity supplement. The hydroxide immediately disappears into the bicarbonate/carbonate system. In other words, the amount of hydroxide present in aquarium water is really only a function of pH (regardless of what has been added), and at any pH below 9, it is an insignificant factor in alkalinity tests (much less than 0.1 dKH). Consequently, the fact that alkalinity is initially supplied as hydroxide is not to be viewed as problematic, except as it impacts pH (see below).
The fact that limewater is very basic (the pH is typically above 12) demands that the limewater be added slowly to an aquarium unless very small additions are made. The reason for slow addition is two-fold: to prevent the local pH in the area of the addition from rising too high (slow addition permits more rapid mixing with tank water to reduce the pH), and to prevent the overall tank pH from rising too high (slow addition allows the tank to pull in CO2 from the atmosphere during the slow addition, mitigating the pH rise). Some aquarists advocate rapid addition, and that is acceptable for additions that would add significantly less than 0.5 dKH of alkalinity to the tank, but an addition of 1.4 dKH (0.5 meq/L; the equivalent of adding 1.2% of the tank volume in saturated limewater or 14 grams of solid calcium hydroxide into a 100-gallon tank) drives the pH of the whole tank too high (up by about 0.6 pH units from where ever it started).
Consequently, limewater is most often added slowly, by dripping or slow pumping. Often it is added as the top off water, replacing most or all of the evaporated water. The pumps add cost and complexity to the system, especially if combined with a float valve or switch (I use the latter and a Reef Filler pump).
As mentioned, limewater has a very high pH. This high pH can have significant advantages with respect to impurities present in the lime. Phosphate and many heavy metals will precipitate, either as calcium salts, or as metal oxides and hydroxides. Copper, for example, may accumulate in some aquaria. Copper hydroxide is very insoluble in limewater because of all of the hydroxide present. From an aquarist’s perspective, there will simply be no copper in clear limewater assuming that it has been given a chance to settle out because copper hydroxide is so very insoluble, regardless of whether there is a copper impurity in the calcium hydroxide solid, or in the source water used. Some aquarists get colored residues in limewater systems, and these colors are coming from metal impurities that did not get into the tank.
Another advantage of limewater may be its ability to reduce the phosphate already in the tank water. While it may be as simple as precipitation of calcium phosphate where the high pH, high calcium limewater meets the aquarium water, the mechanism and extent of this effect in typical reef tanks has not been established.
Another important consideration for limewater is the upper limit to the amount that can be added to an aquarium. The solubility limit of calcium hydroxide in fresh water is about 2 level teaspoons per gallon. If an aquarist has a tank near the high end of calcium and alkalinity demand, then replacing all of the evaporated water with saturated limewater may not be adequate to replace the ongoing losses of calcium and alkalinity. There are a couple of tricks to get a little more from the limewater. These are adding fans to increase evaporation, and adding vinegar to increase the solubility of the lime in the limewater (45 mL of vinegar per gallon of limewater will allow three level teaspoons to dissolve instead of just two). Both of these systems have been successfully employed by many aquarists.
Additionally, the use of a small amount of one of the other balanced additive systems (especially the two/three-part additive systems) in conjunction with limewater is often used by aquarists give a little boost to tanks that need a small amount of extra calcium and alkalinity beyond what limewater can supply, without incurring significant capital costs. Likewise, they can be successfully combined with limewater during periods of low evaporation. Unlike some other supplementation schemes, tank salinity will not increase over time through the use of limewater.
The cost of a limewater system can range from very little to quite a lot. If one uses an inexpensive drip system ($20) and bulk sources of lime the cost can be quite low. Bulk calcium hydroxide available to hobbyists sells for less than $2 per pound (maybe much less in a group buy from a large distributor). The cost per thousand milliequivalents (meq) of alkalinity is on the order of $0.15. I realize that this number means nothing to most aquarists, but I’ll use it to permit cost comparisons of very different supplementation schemes, and at the end of the article, I’ll convert it to yearly costs for some typical tanks. Branded hobby and lab grades of calcium hydroxide will be more expensive. A pound of calcium hydroxide from a well-known hobby company costs about $7, or $0.57 per thousand meq of alkalinity.
Of course, dosing pumps can be several hundred dollars, a good float switch can be $50-100, and one needs to get a reservoir as well (often a plastic container like a trash can; I use 44-gallon Rubbermaid Brute trash cans). Depending on the setup, the limewater reservoir can be far from the tank; even in another room or on another floor of the home. A pump like a Reef Filler or Liter Meter pump can be used to send the limewater significant distances, freeing up space around the tank.
Some people use reactors to deliver limewater. These systems automate the delivery of limewater to the tank, and, of course, the costs rise. They consist of a chamber where fresh water enters, is mixed with solid lime, and the fluid limewater exits the system and travels to the tank. They do not permit any additional calcium or alkalinity to be delivered to a tank compared to other limewater delivery methods (assuming that both use saturated limewater), but many claim them to be less hassle than delivery from a still reservoir. Addition of limewater with the simplest drippers may require daily attention, while delivery from a large reservoir may require attention only once every 1-5 weeks, which is about the same as typical limewater reactors. All of the other comments about limewater apply equally well when used with a reactor, a dripper, or a slow pump from a still reservoir (except that the vinegar/limewater combination is technically difficult to use with a limewater reactor).
On the negative side, limewater does have some concerns that don’t apply to most other systems. One is the effect of overdosing. All calcium and alkalinity additives, if added in sufficient overdose, can case abiotic precipitation of calcium carbonate in the tank. Limewater, however, is especially prone to this effect for two reasons. If overdosed, the high pH of the limewater will rapidly convert much of the bicarbonate in the tank to carbonate, increasing the likelihood of precipitating calcium carbonate. Also, addition of solid lime particles can cause local extreme spikes in pH and calcium that nucleate precipitation of calcium carbonate. Consequently, a limewater overdose, and especially the dosing of lime solids, is by far the most frequent cause of “snowstorm” events where calcium carbonate precipitates all through the water column. In some cases, the tank can look like milk. The good news is that this event usually causes no lasting harm to tank inhabitants unless the amount overdosed is exceptionally large, but it is nearly always upsetting to the aquarist. I’ve had it happen numerous times without losing anything.
Another drawback to systems where the limewater dose is tied to evaporation is that the evaporation may change daily or seasonally. I’ve not found that to be problematic in my system, but others who are more concerned about maintaining a very specific alkalinity may have more trouble with this issue. Dosing limewater on a timed pump rather than to match evaporation may eliminate the concern, as long as it doesn’t exceed evaporation rates.
One final note on lime: The high pH of the liquid and the dust hazard of the solid are not to be treated lightly. Inhalation of the dust is to be avoided. Splashing of limewater onto skin is also to be avoided, and should be followed by extensive rinsing with tap water if it happens. Splashing of limewater into the eyes is especially to be avoided, and the use of safety goggles when using large amounts or in situations where exposure is likely is prudent. Extensive and immediate rinsing with tap water, followed by professional help would be advised in the case of eye exposure.
Calcium Carbonate/Carbon Dioxide Reactors
Calcium carbonate/carbon dioxide reactors work by removing water from the tank, adding carbon dioxide to reduce the pH to about pH 6.5, and then allowing the more acidic water to dissolve solid calcium carbonate media that is present in a mixing chamber. The water is then returned to the tank with its extra calcium and alkalinity (bicarbonate):
CaCO3 + H+ → Ca2+ + HCO3–
Reef tanks employing such reactors typically run at a pH below that of natural seawater, with typical tank pH values of 7.7 to 8.1. The reason for the low pH is the constant delivery of low pH solution to the tank, adding both excess CO2 and bicarbonate. There is no way around this completely, but some reactors incorporate a second chamber, allowing the liquid to pass over additional calcium carbonate media, making better use of the carbon dioxide that is actually added. Aquaria then blow off this extra CO2 and the pH rises, but the effect is typically not complete, and the pH often stays below what would be the case if the same tank water were fully aerated (that is, equilibrated) with normal air.
The media used is important in these systems, with the aragonite form of calcium carbonate being more readily dissolved than the calcite form (although both work). Also, the nature of the impurities can be very important, as nearly all of the impurities will be dissolved and delivered to the tank. Some of these impurities may be desired by the aquarist (such as magnesium and strontium) and some may not be (such as phosphate or copper). Phosphate in reactor media has sometimes become a point of competition between commercial suppliers of media for such reactors, but I would advise aquarists to be skeptical of some of these claims.
One big advantage of these reactors is that they can be scaled to deliver any amount of calcium and alkalinity needed by any tank. For this reason, they are greatly favored by those who have tanks with a high demand for calcium and alkalinity. Because of the low pH that often results, many of these aquarists choose to dose limewater in conjunction with the reactor, not because the reactor cannot supply enough calcium and alkalinity, but purely to raise the pH in the tank itself. The synergy between limewater and CaCO3/CO2 reactors involves more than just pH. Limewater uses up CO2 and CaCO3/CO2 reactors deliver it to the tank. Together, they combine to keep CO2(and consequently, pH) more in line with natural seawater.
Calcium carbonate/carbon dioxide reactors take up a substantial amount of space, since one needs a carbon dioxide cylinder, a reaction chamber, and a pump. Typically, these systems are used close to a tank, but they could be remote if appropriate water flows to and from the tank could be worked out. Once an aquarist has properly adjusted the reactor system, it requires minimal monitoring for a substantial period. Tank salinity will not increase over time using calcium carbonate/carbon dioxide reactors.
The likelihood of problems from overdosing using such a reactor is minimal. Since the pH is typically low, even substantially elevated calcium and alkalinity values may not cause a dramatic calcium carbonate precipitation event. More likely is just slow precipitation onto heaters and pump impellers. Accidental delivery of large amounts of CO2 to the tank is a concern, but that is a rare accident.
The initial costs of such reactor systems can be considerable, typically about $300-600 for the reactor itself, plus additional costs for the CO2 apparatus. Media costs vary, but a bit over $2 per pounds is typical. That puts the media cost at about $0.30 per thousand meq of alkalinity. DIY ground limestone can be used as media for a tiny fraction of this cost, if you can find it locally. The carbon dioxide cost also needs to be figured in, so that might push the total to about $0.40 per thousand meq of alkalinity.
The primary safety concern for these systems involves the carbon dioxide gas cylinder. Any high-pressure gas cylinder can be very dangerous if the cylinder head should become damaged. So be careful to not drop such cylinders least they become rockets.
Two-part Balanced Additive Systems
There are now a plethora of two-part balanced systems for supplementing calcium and alkalinity, as well as DIY recipes that I have published and for which suppliers sell quality DIY ingredients. These are always liquid additives that you add equally to tanks to supplement both calcium and alkalinity. In the DIY version, magnesium is added to the aquarium as a third solution, although it need not be added especially frequently. The rational for this type of product is that the bicarbonate and carbonate that one might like to dose to supplement alkalinity are not readily compatible with the calcium that is also needed. So one portion contains calcium and the other contains the alkalinity. When a DIY is used, the magnesium sulfate in it is not compatible with either part, so it needs its own solution.
In the simplest form, such a system would be provided by any calcium salt at one concentration in one bottle, and a carbonate alkalinity supplement in the other bottle. Within that constraint, manufacturers have a fair amount of room to play. Typically these additives claim go a step further. When the calcium and alkalinity are taken out of the picture, as they will be by calcification in the tank, then the ions that remain are often described as having the same ratios of ions as natural seawater. Assuming that this is true, then the “residue” is simply more salt for the aquarium. Over long periods of time the salinity will build up due to this process (an effect that is quantified below), but there will be no significant buildup of specific ions in the tank.
In order to accomplish this, manufacturers could use a variety of calcium salts in the calcium portion, for example. They could use calcium chloride, calcium sulfate, calcium bromide, and a variety of other similar salts. They could also put magnesium and strontium in this portion as they would not be compatible with the alkalinity component.
The alkalinity portion of these systems is more complicated. As has been shown in other parts of this article, alkalinity can be provided as bicarbonate, carbonate, or hydroxide. I don’t know of any commercial supplements that use hydroxide for a two part system, but the commercial ones do use bicarbonate, carbonate, and mixtures thereof. Consequently the pH varies substantially between brands, and the various brands of these products should not be thought of as identical for this reason, if no other. In order to attain the natural seawater residue, the alkalinity portion could contain sodium bicarbonate or carbonate, potassium bicarbonate or carbonate, lithium bicarbonate or carbonate, etc.
I’ve not seen any independent test of whether these actually produce a residue equivalent to natural seawater, but I’ve seen no particular reason to doubt it, at least for the major ions. When it comes to the trace elements that might concern some reef keepers, it seems unlikely that these products will be any less prone to having uncontrolled levels of trace compounds like copper than are commercial salt mixes, or any other supplement of calcium and alkalinity, but that remains to be determined (at least as far as I know).
One issue that has confused some reef keepers, however, is the presence of trace elements. Assuming that these products are actually formulated with every ion such that a true natural seawater residue remained (let’s call this the “ideal” product), then it will necessarily contain such ions as copper. Since copper is elevated in some reef tanks, and is toxic to many invertebrates, reef keepers have wrongly criticized this method as adding more copper. That’s actually not what would happen. Since these products leave a natural seawater residue, and since copper may be elevated in concentration in many reef tanks relative to seawater, then using these “ideal” products will actually LOWER copper levels because when the increase in salinity is corrected, the copper will drop.
For example:
You have copper in your aquarium at 4 ppb and salinity of S=35.
You add a two part additive that over the course of a month raises salinity to S=36, and raises copper to 4.02 ppb.
Then you correct the salinity back to S=35 by diluting everything in the tank with fresh water, and you get a final copper concentration of 3.9 ppb.
Does this happen in real products and not “ideal” products? I have no idea. But the statement by manufacturers that it contains all ions in natural ratios, including copper, should not be viewed as a concern that it is exacerbating a heavy metal problem.
The rise in salinity of these products over time can be very roughly calculated, though there are several reasons why this calculation is only an estimate. For every 1000 meq of alkalinity added in this fashion (and the matching amount of calcium) these products will deliver on the order of 60 grams of other ions to the tank. In a tank with a low calcification demand (defined later to be 18.3 thousand meq of alkalinity per year in a 100 gallon tank (0.4 dKH/day)) this effect will raise the salinity by 3 ppt per year (compared to a normal salinity of S ~35). In a high demand tank (defined later to be 219 thousand meq of alkalinity per year in a 100 gallon tank (4.4 dKH/day)), the salinity will rise by 35 ppt in a year, or approximately doubling the salinity. Consequently, the salinity should be monitored closely in using these types of additives, especially in a tank with high calcification rates.
Many people have begun to use dosing pumps to deliver these sorts of additives more uniformly across a day/night period with less work by the aquarist. Such pumps can be obtained starting under $100 for each part dosed this way. There is no need to dose the magnesium part this way, since very little is actually required and once a week is plenty often enough.
The costs of these systems vary a bit. The original B-ionic from ESV costs about $34 for 1 gallon of both parts (10,600 meq of alkalinity), or about $3.20 per thousand meq of alkalinity. It has a pH raising effect, similar to my DIY Recipe 1. The B-ionic Bicarbonate version is more expensive, and is necessarily more dilute than is the original because sodium bicarbonate is much less soluble than is sodium carbonate. If your tank pH gets too high using one of them (such as the original B-ionic), then it is reasonable to switch to one that has a smaller pH raising effect (like the bicarbonate B-ionic or my DIY Recipe 2 using baking soda).
The DIY recipes can be far less expensive, depending on what grade of ingredients you use. Buying ingredients from a place such as Bulk Reef Supply will cost roughly $10 per gallon (total cost of all parts, so 1 gallon calcium, 1 gallon alkalinity, and a few cups of magnesium additive), or about $1.40 per thousand meq of alkalinity.
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Joeganja
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I am interested in buying a doser but can't debate on whether I want to dose two part or kalkawasser. Any suggestions? 90 gallon reef. Sps soon to be dominant. What should I dose with 4 dosing pumps?
davidwinn101
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Sps will require lots of calc. You may end up dosing so much so often that a ca reactor is necessary. I have a aquamedic dual doser if needed as well as two Marin 1L dosing containers
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Joeganja
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We'll eventually if I see the doser isn't working I'll get the calcium reactor and use the doser as kalkawasser but I wanna know should I get a doser? I heard they are more stable then calcium reactors. Plus you gotta get a ph monitor.
davidwinn101
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Def not more stable in my experience. Yes they dose on set intervals. Swings are caused by more than time lapse. A reactor and probe allow the unit to turn on and off according to a constant reading not just because said timer goes off
davidwinn101
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Yeah they are initially more expensive but you may find that you go thru so much two part that sooner or later it becomes more of an expense than the reactor would have been. I'd talk with someone local you trust to access your system as far as equipment goes
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FWIW, while davidwin101 obviously prefers reactors, and that is fine and I agree they are a good method, I would not say it is the most commonly used method, even on sophisticated SPS tanks these days. At least in online forums, I think I see somehwat more people using two part systems (or Balling, which is similar) than reactors these days. So check around the forums and see what folks are using in tanks of the month, etc.
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Joeganja
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I see mostly dosers. But then again they add the weirdest crap.FWIW, while davidwin101 obviously prefers reactors, and that is fine and I agree they are a good method, I would not say it is the most commonly used method, even on sophisticated SPS tanks these days. At least in online forums, I think I see somehwat more people using two part systems (or Balling, which is similar) than reactors these days. So check around the forums and see what folks are using in tanks of the month, etc.
