Raising GH/KH

[gzeiger]

I know this has been asked before, but none of the old posts seem to be exactly the information I'm looking for. I have a 75 gallon tank with a fair number of plants, shrimp and snails. I really want the snails to reproduce, and I want to make sure both they and the shrimp have enough calcium for shells. Obviously I also want to make sure the water is adequately buffered.

Right now the water looks like this:
NH3 0
NO2 0
NO3 10
pH 7
GH 6
KH 0 (yes really)

The water out of my tap is a touch over 8.0 pH, so I think I have a problem here. There's no obvious acid source in the tank, although I had planned to add driftwood in the next week or two. The substrate contains a small amount of aragonite which I had hoped would moderate the water hardness, but that plan seems to have failed.

These results follow a 20% water change this morning, so it may have been slightly worse yesterday. What do I need to do to get GH and KH up? I'm ok with raising pH some, since the tank is currently significantly different from the tap water I'll add during water changes, but obviously I'd like the tank to match the tap.

 

[jsoong]

Snails certainly won't do well with KH of 0. Shell is mostly carbonates, if it is not in the water, they won't grow new shell.

The easiest way to raise KH & GH is to add a source of Cacium carbonate into the water. Crush coral is people's favorite, but you can also use crushed oyster shells, crushed limestone ....

If you want a set & forget system, then you add a LOT of cc in the tank (amount doesn't matter). The carbonate will dissolve into the water until it reaches equilibrium (pH of around 7.8 ) . Excess cc will then sit in the tank & acts as a reservoir. Anytime the pH (or KH) drops, more will dissolve in until it reach equilibrium again. Put in more cc when it runs low & you are set.

If the pH of 7.8 is too high for your liking, then you will have to play with adding just a little bit to get to the pH/KH you want. You will have to experiment with the amount & likely the pH won't be as stable as the set & forget system.

 

[gzeiger]

I assume you mean that a pH of 7.8 is the equilibrium provided by crushed coral? That's more or less ideal, since it's actually very close - if anything slightly less basic - than my tap water.

The aragonite I mentioned is crushed coral, which I expected to have the effect you describe. Is it necessary that it be exposed to flowing water? I currently had it as the lower layer of substrate in part of the tank, with regular gravel on top, due to some bottom-dwelling fish that I would prefer not to expose to sharp edges (I have an eel and a couple flatfish).

Crushed limestone seems like it might not be so sharp as the coral. Does it dissolve too readily to make a set and forget system with that?

 

[jsoong]

You have to expose the cc to water for it to dissolve in. Having it in the bottom of your layered substrate might not do the trick.

Do you have room in your filter? You can put a little bag of cc in your filter to avoid the sharp edges in the tank.

 

[gzeiger]

I think there's enough room. I'll give it a try. Thanks.