Alkalinity Dosing Question

[EastEndReefer]

I've owed reef tanks for a few years now and about 6 months ago started a 20 gallon red sea nano max, mainly sps. I've been able to keep my parameters mostly where they should be and as steady as possible. I perform water changes of 5 gallons weekly. I have noticed with this tank that I only have to dose alkalinity and in what "I would assume" is a high amount for a 20 gallon tank. Currently to maintain a steady alkalinity of 9.6, I dose a total of 33 ml a day, spread out over night. My questions are, Is it ok to just dose for alkalinity alone if no calcium dosing is required? Does this happen often?-I of course understand each tanks demands are different. I notice a slight increase in calcium when alkalinity is raised, is that possible?

 

[JMarsh]

I found that when I first started getting a lot of corals in my current tank-primarily when I added an open brain-that my tank started demanding alkalinity, while water changes were keeping the rest of params in check. This was at about 6 months in. A couple months and coral additions later I needed to start dosing calcium.

 

[Randy Holmes-Farley Verified Community Expert]

I've owed reef tanks for a few years now and about 6 months ago started a 20 gallon red sea nano max, mainly sps. I've been able to keep my parameters mostly where they should be and as steady as possible. I perform water changes of 5 gallons weekly. I have noticed with this tank that I only have to dose alkalinity and in what "I would assume" is a high amount for a 20 gallon tank. Currently to maintain a steady alkalinity of 9.6, I dose a total of 33 ml a day, spread out over night. My questions are, Is it ok to just dose for alkalinity alone if no calcium dosing is required? Does this happen often?-I of course understand each tanks demands are different. I notice a slight increase in calcium when alkalinity is raised, is that possible?

Very likely you are using a proportional amount of calcium as well. What is the current calcium level?

You didn't say what you are dosing, just how much, but I'll assume it is something with a potency the same as my DIY (e.g., BRS sells the ingredients).

If that potency is true, then you are dosing about 2.1 dKH of alk per day. That's not excessive if you have substantial coralline growth or growing hard corals, but if not, is on the high side. You are likely using about 13 ppm of calcium a day, but if you are doing a lot of water changes, the water changes might offset the demand.

Personally, I'd dose the balanced amount of calcium if you are using a balanced two part system, unless calcium is already too high (say, 500+ ppm).

There are only a few things that deplete alk and not calcium, but alk always appears to drop faster even when properly baalnced. That's just the math of calcium carbonate in seawater.

Things that cause an alk/calcium demand imbalance are water changes with a mix that does not match the tank parameters, using a sulfur denitrator (it depletes alk), and rising nitrate (that depletes alk, 4.5 dKH per 50 ppm nitrate).

This has more:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

 

[EastEndReefer]

To keep my alkalinity stable right now I’m dosing 33 ml a day in brs sodium bicarbonate. I have not been dosing calcium due to my calcium level being around 500. I guess the weekly water changes keep at 5 gallons keep up the calcium. I’m just afraid to does equal parts, because I have done it before and have had my calcium above range

 

[Randy Holmes-Farley Verified Community Expert]

To keep my alkalinity stable right now I’m dosing 33 ml a day in brs sodium bicarbonate. I have not been dosing calcium due to my calcium level being around 500. I guess the weekly water changes keep at 5 gallons keep up the calcium. I’m just afraid to does equal parts, because I have done it before and have had my calcium above range

Ah, the bicarbonate recipe is half as strong as the carbonate recipe, if made correctly, so you may be dosing only 1 dKH per day. At 1 dKH per day, the calcium decline will be only about 6 ppm per day.

Can you clarify exactly what you did to make the stock solution for alk dosing?

It is fine to let the calcium decline for a bit before dosing any or to dose it proportionally. Both will work fine.

 

[EastEndReefer]

I have always mixed my BRS alkalinity and calcium solutions as per their instructions. At the same time I use their calculator to adjust my levels and use it to figure out how much to dose the tank as it depletes. Is this where I’m in the wrong?

 

[Randy Holmes-Farley Verified Community Expert]

I have always mixed my BRS alkalinity and calcium solutions as per their instructions. At the same time I use their calculator to adjust my levels and use it to figure out how much to dose the tank as it depletes. Is this where I’m in the wrong?

There is some confusion with respect to their proper use of the bicarbonate recipe. Some people get bicarbonate but try to follow the carbonate recipe.

Hence, what exactly did you mix into what volume of water?

 

[EastEndReefer]

I’ve been mixing my alkalinity solution at 1 1/8 cup of dry sodium bicarbonate to 1 gallon of rodi wate, as per BRS. I’m also using Red Sea coral pro salt, for water changes which I understand has higher levels once mixed than the levels currently are in my tank. I appreciate the replies guys.

 

[Randy Holmes-Farley Verified Community Expert]

I’ve been mixing my alkalinity solution at 1 1/8 cup of dry sodium bicarbonate to 1 gallon of rodi wate, as per BRS. I’m also using Red Sea coral pro salt, for water changes which I understand has higher levels once mixed than the levels currently are in my tank. I appreciate the replies guys.

OK, that is the correct recipe, and you are only dosing 1 dKH per day. The expected matching calcium decline is only about 6 ppm per day, and Red Sea Coral Pro does start with high calcium, although I'm surprised it is 500 ppm. In any case, if you have confidence in the calcium measurement, it is fine to dose just the alk part while the calcium declines.

 

[Clownfishy]

OK, that is the correct recipe, and you are only dosing 1 dKH per day. The expected matching calcium decline is only about 6 ppm per day, and Red Sea Coral Pro does start with high calcium, although I'm surprised it is 500 ppm. In any case, if you have confidence in the calcium measurement, it is fine to dose just the alk part while the calcium declines.

I too through 500ppm calcium was high from the new salt mix so I have just tested the water I have just made up with Reef Crystals and that also reads 500ppm and dkh of 12 for alk. I know our test kits are not that accurate (I used Salifert) but I wonder if it is our water changes that are throwing some of our alkalinity out?

 

[Randy Holmes-Farley Verified Community Expert]

I too through 500ppm calcium was high from the new salt mix so I have just tested the water I have just made up with Reef Crystals and that also reads 500ppm and dkh of 12 for alk. I know our test kits are not that accurate (I used Salifert) but I wonder if it is our water changes that are throwing some of our alkalinity out?

Which calcium test kit? How are you measuring salinity?

Water changes will only be adding alkalinity with those mixes and your target level since the mixes are higher than your tank.

 

[Clownfishy]

Salifert calcium kit and using a refractometer

 

[EastEndReefer]

Now obviously over time, keeping my alkalinity stable with dosing, being aware the level of alkalinity will change with stock consumption as more are added and the coral size increase, with water changes the levels in the tank will even out with the levels in the salt mix we are using at the time? Techinically?

 

[Randy Holmes-Farley Verified Community Expert]

Now obviously over time, keeping my alkalinity stable with dosing, being aware the level of alkalinity will change with stock consumption as more are added and the coral size increase, with water changes the levels in the tank will even out with the levels in the salt mix we are using at the time? Techinically?

I'm not sure exactly what you mean by "even out", but the tank alkalinity level is not controlled by the alkalinity in the salt mix used, except that if the salt mix has a higher alk, each water change will also be a small alk boost, and if the salt mix has a lower alk, each water change will give a small alk drop.

Most reefers do not keep alkalinity in their tanks as high as in certain salt mixes (IO, RC, RS Coral Pro, etc.).

 

[Randy Holmes-Farley Verified Community Expert]

Salifert calcium kit and using a refractometer

I'm not sure why your calcium has hit 500 ppm, unless you have dosed it, or one of the measurements is off.

 

[Clownfishy]

I'm not sure why your calcium has hit 500 ppm, unless you have dosed it, or one of the measurements is off.

Thanks for the info, I assumed that was the level RC make it. I will be doing another water change at the weekend so I will give the bucket of salt a bit of a shake just to ensure it is all mixed correctly and test again. I will also borrow my friends refractometer so will test with two of them as I am wondering if my salinity is not quite what I think it is!

Thanks for the information. I really enjoy your responses to the posts as I learn so much

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the info, I assumed that was the level RC make it. I will be doing another water change at the weekend so I will give the bucket of salt a bit of a shake just to ensure it is all mixed correctly and test again. I will also borrow my friends refractometer so will test with two of them as I am wondering if my salinity is not quite what I think it is!

Thanks for the information. I really enjoy your responses to the posts as I learn so much

You're welcome.

I think most people find RC has calcium in the mid 400's, but I wouldn't be shocked if a batch or part of a batch hit 500 ppm, especially with all the uncertainty involved in calcium and salinity measurements.

 

[Mike Reef Addict]

You're welcome.

I think most people find RC has calcium in the mid 400's, but I wouldn't be shocked if a batch or part of a batch hit 500 ppm, especially with all the uncertainty involved in calcium and salinity measurements.

I was having the opposite problem last bag was averaging 320-350ppm calcium (Salifert) and 11°Dkh API. You guys have me wondering what it is at for RC. I have 15g of saltwater that has been mixing since Sunday I'll check it when I get home, I need to toss a heater in it tonight anyway the one that was in it went in the trash lastnight. I'll let you guys know.

 

[EastEndReefer]

I was just assuming that if you maintain a certain alkalinity level, say 9.6 with dosing. That if you are spot on or very close that water changes over time using a salt mixture with a higher dkh, say 12. That eventually the dkh is going to increase
in the tank or equal to the measurement of alkalinity in the salt mixture you use?

 

[EastEndReefer]

And to be completely honest,with what you said, I’m a little hesistant to say or trust what my Hanna checker says my calcium levels are at. But I do know that the Hanna checker I use for alkalinity seems to be spot on