Arkylady & Davey, crushed coral raises the KH. The KH will raise the PH.
An example of how it works: in my 20 gallon high, I use a total of 3 tablespoons. My KH went from1 to 4, then my PH from 6.2 to 7.0. It was total coincidence that my PH ended up being 7.0, I wasn't aiming for that, in fact, all I was aiming for was a KH of 4.
Start with 2 tablespoons and add another every 3-ish days until the KH is around 4, the PH will raise with it. If you PH ends up somewhere in the 7's that ok, it doesn't have to be exactly 7.0, as long as the KH is stable, the PH will be as well.
My first time trying crushed coral, it took me a couple of weeks to get mine right, I started with 2 tablespoons, added another 2, then had to remove some, then add some, remove add.. etc etc.... I didn't give my tank enough time to adapt, and I used too much each time I added. Start with 2, then go form there.
IME, Crushed coral is the only way to go with raising and STABILIZING the PH, via the KH route. chemicals, and baking soda just didn't do it for me. Well, ok, techically they DID raise the PH, but it was always only a temporary solution, and I always had to add more - sometimes daily!
I have been using the same 3 tablespoons of crushed coral in my 20 gallon for 3 months. In my larger tank, the crushed coral has been in the tank for close to a year. I would imagine that eventually the crushed coral would need to be replaced, but I honestly don't have a clue when this happens. Does coral just disolve entirely at some point? Anyone?
Good luck!
