PH drop causing precipitated kalk to leach back out elements?

[Vested]

Heard this theory a few times now and sounds accurate, I don't know the best way to explain it but people saying tanks can crash after using kalk for a long time and then after a ph drop some unknown amount of phosphates and trace elements leach into the water column? Is there any way to know specifically how much of a drop is dangerous and or how fast/sustained?

 

[exnisstech]

but people saying tanks can crash after using kalk for a long time and then after a ph drop some unknown amount of phosphates and trace elements leach into the water column?

I'm not challenging just looking for clarification.
How does this happen exactly? I ask because I have a tank getting 7200ml of kalk dosed daily and it is my most succesful and stable tank I have out of 3.

 

[Vested]

I'm not challenging just looking for clarification.
How does this happen exactly? I ask because I have a tank getting 7200ml of kalk dosed daily and it is my most succesful and stable tank I have out of 3.

Honestly I'm asking for clarification or even validation as well, just heard it most recently from adam at frag garage on the reef dudes podcast. I love kalk personal tank is going through nearly 5000ml a day and hearing this raised some concern.

timestamp

 

[exnisstech]

Doesn't sound too concerning, at least to me. We never have anyone over to bother household pH. I have no plans at this time to go off of kalk and if I have a power outage everything is at risk. Maybe one of the science guys will chime in with their oppinion.

 

[jda]

I have not used kalk in a long time, so some of this is old and some of it is just what I have heard and read...

Kalk does contain impurities. If you mix it and use the clear part and leave the bottom behind, this takes care of most of the impurities. If you add the whole mix, then the impurities enter the tank.

Kalk can bind with some phosphate when in the high pH form to make calcium phosphate which are insoluble at normal tank pH.

While this might be true, there are plenty of things that we use that add impurities, like fish food. Who knows what is in that supplement bottle that people dose - it isn't like reef manufacturers have a track record of being honest or using pure products. Typical export can keep these at reasonable (or zero) levels. I would not be afraid of kalk if you are doing a regular maintenance routine that includes a few different kinds of export including protein skimming and water changes.

I would have to know a lot more about these tanks to know how a pH drop released a bunch of phosphates that kalk is responsible for. ...or even how they had a huge pH drop in the first place. Unless you are adding an acid, then any pH drop is from higher co2 in the room being added into the water again by normal processes (skimmer, surface, etc) bringing the tank pH to where it would have been had you not driven off co2 with the kalk. This is not a pH drop as much as the tank going back to a normal pH.

Dr. RHF is a pro on kalk - I am sure that he will chime in soon.

 

[Vested]

I have not used kalk in a long time, so some of this is old and some of it is just what I have heard and read...

Kalk does contain impurities. If you mix it and use the clear part and leave the bottom behind, this takes care of most of the impurities. If you add the whole mix, then the impurities enter the tank.

Kalk can bind with some phosphate when in the high pH form to make calcium phosphate which are insoluble at normal tank pH.

While this might be true, there are plenty of things that we use that add impurities, like fish food. Who knows what is in that supplement bottle that people dose - it isn't like reef manufacturers have a track record of being honest or using pure products. Typical export can keep these at reasonable (or zero) levels. I would not be afraid of kalk if you are doing a regular maintenance routine that includes a few different kinds of export including protein skimming and water changes.

I would have to know a lot more about these tanks to know how a pH drop released a bunch of phosphates that kalk is responsible for. ...or even how they had a huge pH drop in the first place. Unless you are adding an acid, then any pH drop is from higher co2 in the room being added into the water again by normal processes (skimmer, surface, etc) bringing the tank pH to where it would have been had you not driven off co2 with the kalk. This is not a pH drop as much as the tank going back to a normal pH.

Dr. RHF is a pro on kalk - I am sure that he will chime in soon.

I understand that kalk itself can have impurities but I think this is more referring to kalks (unique?) ability to bind anything in the water to the rocks/surfaces overtime (not just the impurities in itself) and then those releasing at low ph? Im really not sure though lol need a big brain

 

[Randy Holmes-Farley Verified Community Expert]

Heard this theory a few times now and sounds accurate, I don't know the best way to explain it but people saying tanks can crash after using kalk for a long time and then after a ph drop some unknown amount of phosphates and trace elements leach into the water column? Is there any way to know specifically how much of a drop is dangerous and or how fast/sustained?

In my expert chemistry opinion, it is an excuse derived from a lack of chemical knowledge, and the fact that tanks often have problems for reasons we never figure out.

 

[Troylee]

Doesn't sound too concerning, at least to me. We never have anyone over to bother household pH. I have no plans at this time to go off of kalk and if I have a power outage everything is at risk. Maybe one of the science guys will chime in with their oppinion.

I’ve never heard this and not sure I believe it haha! My ph jumps all over the place and never had a issue.. @Randy Holmes-Farley it’s myth busters time!

 

[Vested]

In my expert chemistry opinion, it is an excuse derived from a lack of chemical knowledge, and the fact that tanks often have problems for reasons we never figure out.

Now thats the answer i was looking for haha ~ thanks randy

 

[Randy Holmes-Farley Verified Community Expert]

Calcium carbonate precipitates all the time in most reef aquaria, and the higher the alk and pH, the more likely that is, regardless of what you use to get there.

Calcium carbonate can very slowly redissolve at pH values below around 7.8. So do coral skeletons, and live rock and sand. The effect is very slow, and is not going to introduce anything that wasn't previously in the water to begin with. There's no sudden inrush of chemicals when the pH hits 7.7 or 7.6. To get even a moderate dissolution rate, you need the pH to drop as low as in a CaCO3/CO2 reactor, and in that case, the low pH likely causes organism problems more than dissolved impurities. Evidence: folks do not see any rise in alk from dissolving sand and rock at low pH (say, pH 7.7), so why would anything in the calcium carboante suddenly rise?

I do not see this ever being a cause of a tank crash.

 

[jda]

People also use kalk on tanks with calcium reactors and that water mixed with kalk enters the CaRx where the pH is in the low-mid 6s for pH. No issues here either.

I tried to search for a pH in which calcium phosphate would dissolve and just seemed to learn that this is a complex question with the too-easy-and-probably-not-always-correct answer being around 2? No idea. In any case, looks like this is no issue like I was told a few decades ago.

 

[Randy Holmes-Farley Verified Community Expert]

People also use kalk on tanks with calcium reactors and that water mixed with kalk enters the CaRx where the pH is in the low-mid 6s for pH. No issues here either.

I tried to search for a pH in which calcium phosphate would dissolve and just seemed to learn that this is a complex question with the too-easy-and-probably-not-always-correct answer being around 2? No idea. In any case, looks like this is no issue like I was told a few decades ago.

Yes, it's very complicated, especially since it may not literally be calcium phosphate, but a mix of calcium phosphate and carbonate together.

 

[Vested]

@Randy Holmes-Farley
timestamped, you might find this interesting as an American chemist that disagrees like he says lol