I use Tropic Marin Bio Calcium (under $15 at my LFS
) as an additive for my corals and the rocks. I'm not sure what effect it has on my corals (the first ones I've ever kept) except to say that they are alive and look healthy. My rocks have become so purple that its almost scary. I've been adding it to my 20g reef tank rather conservatively for the past 5 months and since I've been adding it, my rocks keep getting more colorful. It's powder and I add about 1 tbsp every 3-4 days at the most although for the first 2 weeks I got it I added it every day. The LFS
I bought it from uses it in their main coral tank which looks more like a display tank and their LR
(not for sale) is the most colorful I've seen; and some of my rocks are now comparable.
WOW, now that I read what I wrote I sound like a salesman for Tropic Marin or some LFS
, but that's my personal testimony. I had a piece of LR
that had some algae and life on it but was my least colorful rock, and so I put a few of my corals on it, which put a big white spot on it. After taking the coral off and adding the additive, the coralline has grown amazingly well. I can't be certain that this is the cause but I see nothing else to blame. I'm assuming my tank has high calcium levels which I haven't tested recently because of the purple calcium deposits on the glass and the bright colorful rocks.
Well anyways, this is just my personal experience, I hope it helps.