Water Chemistry

Ok, so here's my problem if you want to call it that. About 3 months ago I decided to try a 3g a day water change on my 400g system. Around 8 weeks the SPS started to grow and color up nicely. Over the last 2 weeks or so my ORA Tri-color has went from Cream/Purple/ with green polyps to a REALLY light cream color, not bleach white but no purple and no green polyps. It started out Brown/Purple with green polyps.

My tests are showing 0's across the board, 450 ca and 9 DKH. Can it ...