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Has anyone used guilders whiting (from a pottery supply store) to increase Kh. I am testing it in a fishless tank, and it is doing wonders for increasing my kh without doing much else. Not sure if I am brave enough to drop some cories in yet!

I tried the Chemist in Australia for a pure form and they could order if for $50AU (about $47US). Its only $7 at the pottery supply store for the same quantity.

Same as Plaster of Paris isn't it?

apistomaster wrote:Same as Plaster of Paris isn't it?

No, it's "limestone". I think it will achieve more GH than KH. Bicarbonate of Soda is an excellent KH source.

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Mats

Matts is right about sodium bocarbonate. However, if you intend to use it, sodium bicarbonate will not only increase your KH, but olso your conductivity/TDS. However, that will most likely not be a huge problem.

Another effect can be an increase in pH. Therefore I'd suggest to verify this value before adding dissolved bicarbonate - and not using it solid

When added to water the calcium and the carbonate dissociate, with the calcium contributing to GH, while the carbonates contributes to KH.

The pH and conductivity will obviously rise, but that's the idea.

Should be fine for the cories, but its always nerve-wracking trying something new.

Keep an eye on the pH levels and make sure they don't get too high.

Limestone behaves very predictably: if pH is lower than 7.5 it will dissolve, thereby raising KH (and through that pH) and GH, until pH is 7.5-7.7. The theoretical endpoint of the reaction is pH 8.3, but you will never reach that pH as the reaction slows down the closer to 8.3 it gets, empirically the end pH will be 7.5 - 7.7. The remaining limestone will then act as a buffer reserve, stopping the pH from dropping below 7.5.

I had prepared a mix of 3:1 calcium carbonate:calcium phospate powder at the pharmacy store, using it as an addition to my turtle and tortoises meals and once a week adding a little to the cory fry tank to keep the shells of apple snails, that stays with cory frys, healty. There are cory frys, bristlenose pleco frys and small apple snails in this tank. I saw no side effect on any of the frys.
But as long as I know all catfish like soft water, I use this suplements in very small quantities. Am I doing something wrong?

Can't comment on turtels, but I'd never add any phosphate to a fish tank - phosphate is said to cause blue algae, it is a waste product of food (DNA breaks down to phosphate, just as bone)

I'm with Bas on the phosphate addition - bad idea in general, as the levels of phosphate that occurs in your water due to feeding of the fish will be sufficient if you haven't got a HUGE amount of plants in the tank with very few fish. Certainly nowhere near as much as 25% of the calcium supplement should be phosphate.

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Mats