Alkalinity stability? pH stability? Are they even different?

[Randy Holmes-Farley Verified Community Expert]

No, you are falsely starting with ammonium, not ammonia. The net process from food to nitrate to N2 is zero alk change.

2 mole alk per ammonium or 1 mol alk per ammonia is expected and exactly what is shown in the articles.

 

[Lasse]

No, you are falsely starting with ammonium, not ammonia. The net process from food to nitrate to N2 is zero alk change.

2 mole alk per ammonium or 1 mol alk per ammonia is expected and exactly what is shown in the articles.

I still not get it - IMO - 1 mol NH3 = 1 mol NH4 = 1 mol NO3 according to the number of molecules in each compound which is 6,02214076 x 10²³ for a mol of any substance,

I read the articles that way that It means that 6,02214076 x 10²³ molecules of NH4 that is total nitrified into 6,02214076 x 10²³ molecules of NO3 lose 2 meq in alkalinity and when the same 6,02214076 x 10²³ molecules of NO3 will be denitrified into 6,02214076 x 10²³/2 N2 molecules it will gain 1 meq in alkalinity. IMO - the last article clearly says that the total loss in that system is 1 meq in alkalinity.

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

I still not get it - IMO - 1 mol NH3 = 1 mol NH4 = 1 mol NO3 according to the number of molecules in each compound which is 6,02214076 x 10²³ for a mol of any substance,

I read the articles that way that It means that 6,02214076 x 10²³ molecules of NH4 that is total nitrified into 6,02214076 x 10²³ molecules of NO3 lose 2 meq in alkalinity and when the same 6,02214076 x 10²³ molecules of NO3 will be denitrified into 6,02214076 x 10²³/2 N2 molecules it will gain 1 meq in alkalinity. IMO - the last article clearly says that the total loss in that system is 1 meq in alkalinity.

Sincerely Lasse

the issue is this:

NH3 + H2O --> NH4+ + OH-

to convert ammonia to ammonium, you generate alkalinity (here shown as OH-)

or to go from ammonium to ammonia you lost alkalinity

So a process starting with ammonium or ammonia to get to the same endpoint (N2) will require different amounts of alkalinity.

 

[Lasse]

Yes but as I know it - the nitrification bacteria do not use NH3 - they use NH4 and in pH 8.0 - it is only around 5 % that of total NH3/NH4 that is NH3. At pH 8.3 - its around 15 %. I can agree with you that in water with pH over 8.0 - there can be differences in the alkalinity loss compared in low pH water

However - your way of explaining from food to N2 assumes that all organisms including fish excrete NH3 passively that will be transferred to NH4 in the water column and there is no active transport of NH4 through the gills. There is different viewpoints and theories if the excess nitrogen transport through the fish gills is passive (NH3) or active (NH4). I´m among them that still see it as mainly an active transport - especially in high pH water (as saltwater) because of the lower differences in concentration of NH3. IMO - that the starting point here is mainly NH4 - not NH3. IMO - my experiences in high loaded recirculation fish farms - with both nitrification and denitrification also support this (however in pH around 7).

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

Yes but as I know it - the nitrification bacteria do not use NH3 - they use NH4 and in pH 8.0 - it is only around 5 % that of total NH3/NH4 that is NH3. At pH 8.3 - its around 15 %. I can agree with you that in water with pH over 8.0 - there can be differences in the alkalinity loss compared in low pH water

However - your way of explaining from food to N2 assumes that all organisms including fish excrete NH3 passively that will be transferred to NH4 in the water column and there is no active transport of NH4 through the gills. There is different viewpoints and theories if the excess nitrogen transport through the fish gills is passive (NH3) or active (NH4). I´m among them that still see it as mainly an active transport - especially in high pH water (as saltwater) because of the lower differences in concentration of NH3. IMO - that the starting point here is mainly NH4 - not NH3. IMO - my experiences in high loaded recirculation fish farms - with both nitrification and denitrification also support this (however in pH around 7).

Sincerely Lasse

In a closed system like a reef tank, it makes no difference exactly what ammonia forms are excreted by fish or later used. They interconvert instantly, with alk changes on each conversion.

What matters is what form is actually produced by metabolism of foods. Fish and other organisms cannot retain significant alkalinity. So if they internally produce ammonia and then it instantly gets converted into ammonium, alk is generated and excreted.

Aerobic metabolism of neutral organic molecules results in ammonia, not ammonium, as the simplest direct product.

I'll show the reaction of a single amino acid, but it applies to all neutral (or zwitterionic) organic molecules of any kind (we are ignoring unusual things like sulfur-containing compounds, etc.):

glycine + O2 --> carbon dioxide + ammonia + water

CH2(NH2)CO2H + 2O2 --> 2CO2 + NH3 + H2O

Of course one can show that as producing ammonium, but then alk is clearly generated (by taking up H+):

CH2(NH2)CO2H + 2O2 + H+ --> 2CO2 + NH4+ + H2O

So either you produce ammonia, or ammonium plus alk.

 

[calli]

@Randy Holmes-Farley do you think that we should be paying more attention to the environmental carbon dioxide levels our tanks are exposed to? I recently bought at CO2 meter and was surprised by how high my Indoor CO2 is.

I think so 100%, I have a low Ph problem right now and I think my issue may be the levels in the room. I have tried everything, and the tank sits in our main room where, we all sit and watch tv, movies, and get togethers.

That being said, now your skimmer may actually be causing some of the problem with high co2 in the water. The gas exchange happens as always, however, now its bringing more co2 filled air into the tank as well.

 

[calli]

I know that I am guilty of mentioning to Randy just a couple of days ago, that I had no idea what my pH was because I wasn't going to "chase it" any way (kind of feel like my comment helped spur this thread). I have since calibrated and placed my pH monitor on the tank so at least I know what the value is. I think the biggest issue that I have, and I'm sure many others, with trying to stabilize pH is that, at least to my knowledge, there is no easy, cheap way to control it accurately and effectively in many cases.

The best option for me was to have my skimmer draw in fresh air from outside, but this only raised the pH. There were still swings from day to night. My current tank sits in the middle of the house and there is no way for me to draw in fresh air. I try to leave windows open, but it is getting VERY hot here (it will be 100 this weekend) so this is no longer an option.

I did switch to dosing soda ash, throughout the day and night, instead of baking soda in order to raise and keep pH higher, but what else can be done to make pH more consistent? Today my pH got up to 8.16 and is currently at 8.05 (its midnight now).

Have you considered a scrubber? Then once you can get you pH up you can use a controller to dose kalkwasser when your ph is lower and stop when it reaches a set point you wish.

Telegram Reefer is doing something like this, but using a much higher concentration of Kalk they call "Slurry". Not suggesting you try that, but the way he controls his dosing is based on pH.

 

[calli]

I am new to hobby. Struggling to understand and get correct. So frustrating. In the last six months I’ve read probably 500 articles/posts/blogs joined several groups on Facebook and watched hundreds of youtube videos on reefkeeping. Probably gonna sound really dumb to most people that are advanced in this hobby but I’m struggling. Idk what I’m doing wrong. My alk tested 12-12.5 I tested twice with brand new salifert kit good till 2024 (Hanna alk check on order thank god) ca 550 mg 1290 but can’t get my ph over 8.0. I did a 5 gal water change hoping that helps. I have a RSM 130d.

A water change will only cause temporary changes to pH. pH is about the co2 concentration in the air around the tank.

You can do things like run an airline outside through a window or wall to have your skimmer bring in air there. You could also dose Kalkwasser as your ALK/CA replenishment, add a co2 scubber to your skimmer. A big one cost wise is to get an air exchanger if the issue is excess co2 in your room.

Your ca is a bit high and your mg is a bit low, but slowly bring those back.

 

[Biologic]

Question -- not sure if it was explicitly mentioned, we know that pH fluctuates in reef lagoons. However, does Alkalinity significantly fluctuate? From my understanding, based on what's being said, yes it would depending on time of day.

 

[arking_mark]

Question -- not sure if it was explicitly mentioned, we know that pH fluctuates in reef lagoons. However, does Alkalinity significantly fluctuate? From my understanding, based on what's being said, yes it would depending on time of day.

Not really. pH just changes speciation of Alk.

 

[Biologic]

Not really. pH just changes speciation of Alk.

Ah right that makes sense. But has stable alkalinity been measured and observed ?

 

[arking_mark]

Ah right that makes sense. But has stable alkalinity been measured and observed ?

"The salinity normalized alkalinity (NTA=TA×35/ S) in subtropical gyres between 30°S and 30°N is remarkably invariable except in upwelling areas (e.g., the Eastern Equatorial Pacific)."

 

[Lasse]

In a closed system like a reef tank, it makes no difference exactly what ammonia forms are excreted by fish or later used. They interconvert instantly, with alk changes on each conversion.

What matters is what form is actually produced by metabolism of foods. Fish and other organisms cannot retain significant alkalinity. So if they internally produce ammonia and then it instantly gets converted into ammonium, alk is generated and excreted.

Aerobic metabolism of neutral organic molecules results in ammonia, not ammonium, as the simplest direct product.

I'll show the reaction of a single amino acid, but it applies to all neutral (or zwitterionic) organic molecules of any kind (we are ignoring unusual things like sulfur-containing compounds, etc.):

glycine + O2 --> carbon dioxide + ammonia + water

CH2(NH2)CO2H + 2O2 --> 2CO2 + NH3 + H2O

Of course one can show that as producing ammonium, but then alk is clearly generated (by taking up H+):

CH2(NH2)CO2H + 2O2 + H+ --> 2CO2 + NH4+ + H2O

So either you produce ammonia, or ammonium plus alk.

OK - you are looking at the problem from a system point of view - and of cause - its the way we should look at it. However - I have experiences of fresh water systems where - when nitrification and denitrification is in balance (the figures for both NH4 and NO3 is constant to each other during time) and still have seen a steady drop in pH that has to be compensated for through adding HCO3. I wonder if there is other factors in the fish, or pathways of inorganic C for the autotrophs. that contradict/work against the alkalinity formation inside/outside the fish when processing the food from a holistic point of view. I admit - I have difficulties to recognize such factors in freshwater but there is at least one important factor in saltwater fish that can make your calculations around alkalinity stability not be the whole truth in an holistic point of view.

For me - itthere is indications that at least the second stage bacteria in the nitrification process do not take up inorganic C directly as CO2. The nitrification process will totally halt in low pH - (rich in CO2) water but works perfectly in high pH (low CO2 content but more HCO3 content) It is also an experience for me that if you rise the alkalinity to around 2-3 in KH in fresh water (around 1 meq) and lower the pH with CO2 - nitrification works in spite of low pH - Is KH below 1 before adding CO2 - nitrification halt IMO. I know we have discuss this before - but it is still a paradox for me.

To start with fresh water fish - I have one experiences that indicate you are right - at least to some degree - according the total sum of alkalinity. I have been working with a lot of people with "crazy" ideas during my time here on earth. One of the more interesting experiences (according to this discussion) is a friends idea that if we did everything we could to inhibit nitrification and let the water accumulate NH4 - it could be a good way for a fish farm system. Its a well-known fact that low pH (read low alkalinity) both block nitrification and forming of toxic NH3. The idea was simply to keep the pH around 6.6 - 6.8 and have a heavy aeration in order the get CO2 out. The pH was stabilised through adding acids. The interesting thing in this was that we need to ad acids all the time because the tendency during time was that the pH rise. The fish was heavily feed during this time. This example will in my book talk fot your ideas. However after a while - We recognize that it was to risky. there was huge amount of ammonium concentrated in the water and slight rise in pH would bring a disaster and even to low pH could kill the fish. We use natural water with some aluminium in it and had one occasion of Al toxicity because pH get lower than 6.5 once.

However - is it the same for salt water fish in a holistic point of view ( Fish physiology and water chemistry as a whole system with interactions in different ways)

Let us assume that the fish secretes NH4 and therefore the increase in alkalinity takes place inside the fish in connection with digestion. A blood/plasma pH rise will result in a higher proportion of HCO3 that's need to be excreted in order to held blood/plasma pH constant. Normally - we assume that this happens in the gills - but saltwater fish seems also have an other pathway for HCO3 secretion that will lead to acidification in both blood/plasma and outside water. Salt water fish drinks and they need to handle the high concentrations of both calcium and magnesium in the digestive tract. At least in some saltwater species it has been shown that this problem is solved through secretion of HCO3 into the digestive tract and a following precipitation of calcium and magnesium to calcium carbonate and magnesium carbonate. Here is one link

If we see this as a whole system - food - nitrification - denitrification - HCO3 secretion - calcium precipitation and so on - it may not be zero sum game in the end - at least not for salt water fish

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

OK - you are looking at the problem from a system point of view - and of cause - its the way we should look at it. However - I have experiences of fresh water systems where - when nitrification and denitrification is in balance (the figures for both NH4 and NO3 is constant to each other during time) and still have seen a steady drop in pH that has to be compensated for through adding HCO3. I wonder if there is other factors in the fish, or pathways of inorganic C for the autotrophs. that contradict/work against the alkalinity formation inside/outside the fish when processing the food from a holistic point of view. I admit - I have difficulties to recognize such factors in freshwater but there is at least one important factor in saltwater fish that can make your calculations around alkalinity stability not be the whole truth in an holistic point of view.

For me - itthere is indications that at least the second stage bacteria in the nitrification process do not take up inorganic C directly as CO2. The nitrification process will totally halt in low pH - (rich in CO2) water but works perfectly in high pH (low CO2 content but more HCO3 content) It is also an experience for me that if you rise the alkalinity to around 2-3 in KH in fresh water (around 1 meq) and lower the pH with CO2 - nitrification works in spite of low pH - Is KH below 1 before adding CO2 - nitrification halt IMO. I know we have discuss this before - but it is still a paradox for me.

To start with fresh water fish - I have one experiences that indicate you are right - at least to some degree - according the total sum of alkalinity. I have been working with a lot of people with "crazy" ideas during my time here on earth. One of the more interesting experiences (according to this discussion) is a friends idea that if we did everything we could to inhibit nitrification and let the water accumulate NH4 - it could be a good way for a fish farm system. Its a well-known fact that low pH (read low alkalinity) both block nitrification and forming of toxic NH3. The idea was simply to keep the pH around 6.6 - 6.8 and have a heavy aeration in order the get CO2 out. The pH was stabilised through adding acids. The interesting thing in this was that we need to ad acids all the time because the tendency during time was that the pH rise. The fish was heavily feed during this time. This example will in my book talk fot your ideas. However after a while - We recognize that it was to risky. there was huge amount of ammonium concentrated in the water and slight rise in pH would bring a disaster and even to low pH could kill the fish. We use natural water with some aluminium in it and had one occasion of Al toxicity because pH get lower than 6.5 once.

However - is it the same for salt water fish in a holistic point of view ( Fish physiology and water chemistry as a whole system with interactions in different ways)

Let us assume that the fish secretes NH4 and therefore the increase in alkalinity takes place inside the fish in connection with digestion. A blood/plasma pH rise will result in a higher proportion of HCO3 that's need to be excreted in order to held blood/plasma pH constant. Normally - we assume that this happens in the gills - but saltwater fish seems also have an other pathway for HCO3 secretion that will lead to acidification in both blood/plasma and outside water. Salt water fish drinks and they need to handle the high concentrations of both calcium and magnesium in the digestive tract. At least in some saltwater species it has been shown that this problem is solved through secretion of HCO3 into the digestive tract and a following precipitation of calcium and magnesium to calcium carbonate and magnesium carbonate. Here is one link

If we see this as a whole system - food - nitrification - denitrification - HCO3 secretion - calcium precipitation and so on - it may not be zero sum game in the end - at least not for salt water fish

Sincerely Lasse

There certainly are other situations where pH and alk are depleted (and alternatively, others where they are added).

For example, water changes that tend to remove nitrate will slowly deplete alk. Dissolution of sand will add alk and calcium, etc.

Certainly there is some precipitation and/or dissolution of calcium carbonate in organisms. Regardless of the reasons for it, I would just lump that with the even larger impacts of biological (skeletal) and abiotic deposition of calcium carbonate.

 

[ReefChasers]

While I can appreciate this discussion and the additional scholarly articles on recirculating systems that @Lasse provided, it is still no explanation for my current (on going) now 700ml of Calcium Chloride daily dosing in the 1200g system when alkalinity is only being supplemented by Kalkwasser.

I understand that the loss/gain of nitrates through biological processes can affect the Alkalinity, but I see no possible way it could be effecting alkalinity this much since we have not dosed any nitrates in now 2 weeks+ and that our nitrate has only shifted between 3ppm-5ppm.

Not really looking for an answer because these systems are so complex that it seems impossible to point to exactly what could be the cause of something like this and there are so many variables at work (known and unknown) that it seems difficult to quantify.

 

[Lasse]

I understand that the loss/gain of nitrates through biological processes can affect the Alkalinity, but I see no possible way it could be effecting alkalinity this much since we have not dosed any nitrates in now 2 weeks+ and that our nitrate has only shifted between 3ppm-5ppm.

How much did you dose of Nitrate on a daily base?

Sincerely Lasse

 

[ReefChasers]

We dont dose it daily but occasionally dose it if an adjustment is needed. We try to use natural feed to maintain as often as possible.

Around 2 weeks ago we dosed the system up 2ppm which was around 1000ml of hobbyist stength.

 

[Lasse]

It will be 9.1 g NO3 added - it means around 0.15 mole NO3 - with Randys calculations it will give a rise with 0.15 meq in alkalinity. 0.15 meq = around 0.4 in dKH - if I have understand things right

Sincerely Lasse

 

[ReefChasers]

We are 8.3 stable now on pH in our primary stony coral system. Night time low 8.28 day time high 8.34. It tends to run a little higher on saturdays and sundays when the facility doesnt have very many humans around (hit 8.37 toda). Alk has stayed steady at 8.6 for the past couple weeks. It just took some additional patience to inch the ph upward.

We are now at 46,000 ml of Kalkwasser dosing in the night time hours on 1200 gal system. Basically we are at our evap limit on that one so probably looking randys new high ph recipes from here~

We are still inexplicably dosing an extra 600ml of calcium chloride daily to hold calcium at 425.

All stats including nutrients have been stable now (ph/alk/ca/nitrate/phosphate) and we are really noticing the effects of the added ph stability.

I am not sure if we will see a growth benefit of pH stability @ 8.3 but we have another extremely stable system which is also in peak health @ 8.1 ph so it will be nice to see how both compare to eachother over a longer period of time.

 

[LimestoneCowboy]

Well, your tank may very well use them in the expected proportion, it is just that limewater (kalkwasser) does not provide the right ratio. I used kalkwasser for 20 years, and I selected a low calcium/high alk mix (normal IO) for that very reason: it provides excessive calcium, as you observe.

The reason for this effect is that kalkwasser provides exactly the ratio of pure calcium carbonate, but in seawater or reef tanks, magnesium, and to a smaller extent, strontium, replace calcium in some of the deposited solids. Thus for a given alkalinity consumed, slightly less calcium is used that that unused calcium is why it rises over time when maintaining alkalinity exactly with kalkwasser.

Would it be feasible to alter a Kalk mix say with something to bump the alkalinity to offset this a bit @Randy Holmes-Farley ?