Awhile ago I started a post about my inability to raise my ca levels above 350 no matter what product I used. (and I tried several!) Reef runner suggested that it may have been the salt I was using (it was Instant ocean) Since switching to Tropic Marin I have had no problem maintaining my Ca at 400 to 425. My clam is very happy!! Just wanted you to benefit from all of my headaches!
I think everytime I did a water change I placed my tank further behind and could not "catch up" with my ca level.
