SPS are tricky, and require nearly perfect water. Some things I have had to consider when keeping these amazing corals are: Flow, I have increased to 7000gph in my main tank which is 75 gallons. Lighting/ coral placement. Knowing the exact species always helps. I have a heavy nutrient import, and aggressively skim with a heavily rated skimmer the unwanted out. Test for phosphates and nitrates. I have Zero reaction for phospates using Saliferts test. Nitrates hover around 5 ppm, which has ill effect on my corals. Consistency, and stable salinity, ph, dkh, CA, and mg. I keep my dkh elevated around 11-12 dkh, CA 420+, ph 8.1, SG 1.025 & MG 1250+ I use an auto top off for evaporation, and also drip kalk for 8 hours a night, w/ about a drip every 2 seconds. With all this said, many SPS gurus such as myself have different approaches to the hobby. I doubt many of the successful ones will disagree with the fact that most of these minimul guidlines should be met or exceeded to have a colorful SPS reef. Some feed their corals state of the art nutrients like probidio, zeovit, aminos, etc.. While others have large fish communities that supply the corals with fish pooh for feeding. Some use a calcium reactor with monitoring systems to stabilize CA, DKH & PH. I personally use kalk, and buffer with 2 part as needed. I also have a refugium on reverse light cycle to help keep my ph stable. Sorry for the lengthy reply, but I have learned the hard way too, and it always sucks when you lose a coral. Good luck.....
