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Aqua-soil and RO water: is a KH booster needed?

Forever Fishtank

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I am trying to better understand the need (or not) of adding KH booster when remineralizing RO water in a tank with aqua soil and CO2. Currently, I don’t add any - it is not a CRS tank by the way, just plants and fish. The reason is, I read that aqua soil contains acid buffers to lower pH. These acid buffers that will take the KH to 0 by binding any KH booster that I add. Thus, adding KH booster will simply serve to deplete the acid buffers I paid for.

I am trying to understand how stable the pH is in a system that only has acid buffers - especially one with co2. Based on my internet research (I am not a chemist and my university chemistry courses are a dim memory) I understood that KH (I guess more appropriately alkalinity buffers) is what stabilizes the pH, countering organic acids and CO2. In the case of aqua soil, does that mean that the same role is carried out by the acid buffers in the soil? But how? I am not clear as to why my pH is not simply crashing to crazy low levels with no KH in the system. Perhaps it is?

One of my problems is that I can't seem to measure my pH properly. High range API liquid test says it is below the lowest range of the test. Low range API test shows it as being higher than the test's highest range. Similar issues with the Fluvial test kits. Some people suggested this means the pH is neutral, but I very strongly doubt that. For example, Tetra test strips show my pH as being 6.2 or lower. How much lower, I have no idea.

In summary, should I add KH buffers?
 

dw1305

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Hi all,
I am trying to understand how stable the pH is in a system that only has acid buffers
It won't be stable at all. Have a look through <"Still very confused about KH and...."> and linked threads.
Thus, adding KH booster will simply serve to deplete the acid buffers I paid for.
It will.
In summary, should I add KH buffers?
Unless you keep <"black water"> fish? I would buffer the water to about 2dKH probably using <"potassium bicarbonate (KHCO3)">.

cheers Darrel
 
Last edited:

Zeus.

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1611056787893.png


I would say toss one and a half teaspoons in tank for a 100l RO WC. @Forever Fishtank post your RO WC volume and will post the result.
(First screenshot of the new Remin calculator I've been working on - targets kGH instead of Ca and Mg like in the present IFC calculator, enables the easier use of all the Ca/Mg salts when targeting dGH. Plus gies the resultant Ca:Mg:K ratio)
 

Forever Fishtank

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Hi all,

It won't be stable at all. Have a look through <"Still very confused about KH and...."> and linked threads.

It will.

Unless you keep <"black water"> fish? I would buffer the water to about 2dKH probably using <"potassium bicarbonate (KHCO3)">.

cheers Darrel
Thanks Darrel. That is what I was thinking as well. However, see <this link by Dennis Wong,> who argues that 0 KH is no problem - but does not explain why:

"SHOULD I BUFFER MY AQUASOIL TANK TO RAISE THE PH/KH?
No you should not if you are keeping soft water livestock/plants. Plants do not use KH and most plants actually function better at low ranges, as does most soft water fish. Many buffers also make use of Phosphate based chemicals that will raise your PO4 levels significantly. Working against aquasoils is counter productive."


He also mentions, <in this article>, that KH stability is very important. I do agree with him on that. Therefore I think adding KH supplements to Aquasoil can be an issue where the KH continually swings from some value to 0 on a weekly basis. I guess he is trying to say that pH does not matter: let it collapse; so what. I just don't have enough chemistry background to really get that though.

I'd love to hear your thoughts.

The reason I am asking is I am about to build a 120G tank, as I mentioned in the Apistogramma forum. I am trying to decide the substrate, and I am uncomfortable using something I don't understand. Therefore I am considering using eco complete instead of aquasoil. I am wondering if I am making a mistake, because of ignorance on my part and that I should go with aquasoil.
 

Forever Fishtank

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View attachment 160927

I would say toss one and a half teaspoons in tank for a 100l RO WC. @Forever Fishtank post your RO WC volume and will post the result.
(First screenshot of the new Remin calculator I've been working on - targets kGH instead of Ca and Mg like in the present IFC calculator, enables the easier use of all the Ca/Mg salts when targeting dGH. Plus gies the resultant Ca:Mg:K ratio)
Thanks for this Zeus. Quite impressive. Are you making this calculator available for public use?

My current tank gets 10L water changes daily, for total of 70L over the course of the week. Tanks size is 150L. My next tank that I am moving everything into is 500L. I'll be doing 35L water changes daily.
 

Zeus.

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The IFC calculator already does remineralising agents you can target NO3,PO4,K,Mg,Ca, dKH and Fe in the 'Targetcalculator' sheet which works out the grams needed for each salt- just select ''bespoke remin'
1611306269164.png
and and its goes into 'Remin -mode'
Or in the 'DIYcalculator' sheet
1611306382563.png

Takes the Grams to ppm/dKH into 'Remin' mode also.

The new 'Remin sheet' I am currently working on just has a few extra tweaks I've been working on and is still in the 'concept' stage of development, it will be months before it is release 'if' it is release/added at all ;)
 

dw1305

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Hi all,
Dennis Wong ("2hr Aquarist") said:
"SHOULD I BUFFER MY AQUASOIL TANK TO RAISE THE PH/KH?
No you should not if you are keeping soft water livestock/plants. Plants do not use KH and most plants actually function better at low ranges, as does most soft water fish. Many buffers also make use of Phosphate based chemicals that will raise your PO4 levels significantly. Working against aquasoils is counter productive."
It needs a bit of unpacking.
  • "Plants do not use KH and most plants actually function better at low ranges": Some plants can use HCO3- <"as a carbon source">, but generally you can grow a larger range of plants in soft water. For those <"that don't thrive">, I don't know whether it is a calcium (Ca) or bicarbonate effect.
  • Same for fish, you would need to choose the fish you keep carefully and keep away from Rift Lake Cichlids etc.
  • Phosphate buffers are a bit of a red herring, that is a <"different kind of buffering"> to dKH, but I'd agree they don't perform any useful purpose.
  • "Working against aquasoils is counter productive": Agreed, you are giving with <"one hand and taking away with the other">.
Therefore I think adding KH supplements to Aquasoil can be an issue where the KH continually swings from some value to 0 on a weekly basis. I guess he is trying to say that pH does not matter: let it collapse; so what. I just don't have enough chemistry background to really get that though.
Yes, this is where I'm not sure. I've always added an equal amount of dGH / dKH (either deliberately or in our rainwater) via CaCO3, so dGH and dKH have always been linked.

Another reason for me is that I like snails, and water with some dGH/dKH is required to keep even <"the most acid tolerant of snails">.

cheers Darrel
 
Last edited:

Forever Fishtank

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The IFC calculator already does remineralising agents you can target NO3,PO4,K,Mg,Ca, dKH and Fe in the 'Targetcalculator' sheet which works out the grams needed for each salt- just select ''bespoke remin' View attachment 161084 and and its goes into 'Remin -mode'
Or in the 'DIYcalculator' sheet View attachment 161085
Takes the Grams to ppm/dKH into 'Remin' mode also.

The new 'Remin sheet' I am currently working on just has a few extra tweaks I've been working on and is still in the 'concept' stage of development, it will be months before it is release 'if' it is release/added at all ;)
Thanks a lot. I’ll make one use of this
 

Forever Fishtank

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Hi all,
Dennis Wong ("2hr Aquarist") said:

It needs a bit of unpacking.
  • "Plants do not use KH and most plants actually function better at low ranges": Some plants can use HCO3- <"as a carbon source">, but generally you can grow a larger range of plants in soft water. For those <"that don't thrive">, I don't know whether it is a calcium (Ca) or bicarbonate effect.
  • Same for fish, you would need to choose the fish you keep carefully and keep away from Rift Lake Cichlids etc.
  • Phosphate buffers are a bit of a red herring, that is a <"different kind of buffering"> to dKH, but I'd agree they don't perform any useful purpose.
  • "Working against aquasoils is counter productive": Agreed, you are giving with <"one hand and taking away with the other">.

Yes, this is where I'm not sure. I've always added an equal amount of dGH / dKH (either deliberately or in our rainwater) via CaCO3, so dGH and dKH have always been linked.

Another reason for me is that I like snails, and water with some dGH/dKH is required to keep even <"the most acid tolerant of snails">.

cheers Darrel
Thanks. I guess I have two choices for my upcoming tank. Go with eco complete or stick with aqua soil and add bicarbonate. I also like snails, as well amano shrimp. The only reason I am not abandoning the aqua soil idea is the incredible reaction fish seem to have to the water parameters created by aqua soil with RO. All the fish are reproducing with no effort on my part - rasboras, apistogramma and panda cories have all had fries in the aqua soil tank with no KH. Perhaps Eco complete with my tap water - 7.6 pH - will have the same results? Choices, choices ...
 

dw1305

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Hi all,
The only reason I am not abandoning the aqua soil idea is the incredible reaction fish seem to have to the water parameters created by aqua soil with RO. All the fish are reproducing with no effort on my part - rasboras, apistogramma and panda cories have all had fries in the aqua soil tank with no KH.
I'm not surprised, very soft water often stimulates spawning in soft water fish. They tend to breed at the start of the rainy season, when there will be more food and shelter available in the seasonally inundated forests and grassland.

A large volume, cool, soft water change is used to stimulate breeding for <"Corydoras spp. and "L" numbers">. If I had softer rainwater I'd try some of the more "black water" fish, <"but even our rainwater"> has some dKH/dGH.

I've <"nearly always"> used (fairly fine) silica sand as a substrate in more recent years.

cheers Darrel
 

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