 Re: CALCIUM
If your calcium levels go too high, you will get precipitation of Calcium Carbonate. This will reduce the carbonate available in your tank. Coralline algae on your rock will want a 1:1 balance of calcium and bicarbonate/carbonate per mole or molecule.
There are four possibilities:
Ca too high/Alk too low: This will also cause poor growth. If calcium is high enough, it will precipitate out with carbonate to form calcium carbonate "white snow" on your sand and rock, and is useless to you. You need to slowly & steadily raise your hardness with baking soda.
Alk too high/Ca too low: This will also cause white snow. You need to steadily drip kalk until your calcium and alk levels are within acceptable ranges.
Alk too low/Ca too low: This is easiest to fix. You won't see white snow, but your coralline growth will be poor. Keep dripping kalk, and separately add your baking soda - possibly in your top-off mix.
Ca too high/Alk too high: This rarely happens, since calcium carbonate will precipitate rapidly out of the water as mentioned in the first two cases. This will "spend" both calcium and alkalinity. In other words, this is somewhat self-correcting. If you're lucky, you will be left with a balance of each and will be happy. Usually though, you will have more of one than the other and you will be left with one of the first two cases.
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