Hi there. I could use some help and suggestions. My Tank: Its about 4 months old (yes its kinda new) 225 gallon 125 sump (large fuge with Kessil H380) Radion Gen 4 pro's Set to AB+ Running Triton Method and have been using ICP tests to back up water parameter testing. Using Apex system including DOS for tank monitoring. PH hovers at 8.0 Alk is fairly stable at 8.5 dkh Mag/Calc 1350/450 I cannot get any phosphate or nitrate readings using Salifert's test kit. Using TropicMarin Salt Fish: (one of each) Yellow tang, purple tang, cleaner wrasse, hippo tang, purple fire fish, and flameback angel. The tank is full of 1" frags of all kinds Issue: SPS (acro's and Monti's) arent doing well. They are surviving but not thriving. Acro's had an initial issue when I used too much GFO to get Phosphates down. That shocked them. That was 2 months ago. Caused most, if not all Acro's to pull their polyps in. Time has passed and I have done some water changes but they really havent fully rebounded. Recently (past 2 weeks) the monti's have started to show some stress. Polyps are not extending much and some bleaching. Even my green birds nest is looking a little bleached (it was thriving and doing great). My initial (and anecdotal) thoughts: 1. Nitrates are too low -- starving the corals -- I have started to feed twice a day for the past 2 weeks. Also adding more fish. They are in QT now doing TTM. 2. Triton DOS chemicals are somehow an issue (not sure how...but a possibility) 3. I had 2 large blocks of MarinPure in the sump. I pulled those out about a week ago. I suspected they may be eating too much Nitrate. -- Final thoughts: When I first add my sps corals to the tank, they took off and grew rapidly. Encrusted and colors where popping. That did not last but about 2 months. Something went wrong and I am scratching my head. I did a 15% water change 3 days ago (nothing changed) and plan a possible 2nd water change of the same volume tomorrow. I also plan on doing another ICP test. Any thoughts are welcome and thanks in advanced.