eschaton
Fishaholic
I have a 40 gallon planted tank that has been going quite nicely, with two exceptions: There was a bit of a black brush/beard algae problem, and many of my snails were experiening shell erosion. The common cause of both was PH that was generally very acidic (in the 6.0 to 6.4 range). This is mostly because of C02 ferting, though the tanks tended towards acidic water for quite awhile beforehand.
Anyway, after much reading online, I realized a more neutral to alkaline PH would be much better, and the best way to buffer it was to add some crushed coral to my filter. I added around three handfills to each filter - enough to replace the now removed carbon layer of my filter, but still keep the organic filter media below water.
I did my first PH test today, and the PH of the tank is now around 8.6 or 8.8! This is kind of shocking to me. The guy at the LFS (usually pretty knowledgeable) said that that would be the max PH you would get if you used the coral as a substrate (such as a ciclid tank) but that it shouldn't alter the PH more than 0.4 in small quantities.
Anyway, there are no apparent negative effects on my fish, even given the huge PH swing. A PH this high will certainly arrest snail shell erosion, and will hopefully cure the algae problem. However, with the exception of some guppies, there is nothing in the tank that perfers alkaline water. Should I remove some of the coral now? And as the coral continues to lose effectiveness, how much should I add in order to raise the PH to neutral without pushing it into cichlid territory?
Anyway, after much reading online, I realized a more neutral to alkaline PH would be much better, and the best way to buffer it was to add some crushed coral to my filter. I added around three handfills to each filter - enough to replace the now removed carbon layer of my filter, but still keep the organic filter media below water.
I did my first PH test today, and the PH of the tank is now around 8.6 or 8.8! This is kind of shocking to me. The guy at the LFS (usually pretty knowledgeable) said that that would be the max PH you would get if you used the coral as a substrate (such as a ciclid tank) but that it shouldn't alter the PH more than 0.4 in small quantities.
Anyway, there are no apparent negative effects on my fish, even given the huge PH swing. A PH this high will certainly arrest snail shell erosion, and will hopefully cure the algae problem. However, with the exception of some guppies, there is nothing in the tank that perfers alkaline water. Should I remove some of the coral now? And as the coral continues to lose effectiveness, how much should I add in order to raise the PH to neutral without pushing it into cichlid territory?
that doesn't sound particularly like a "small" quantity to me. i'd definitely suggest removing some of it and doing some water changes. maybe try only one handful per filter. 
