Steve, I 've had the same problem you describe with my (former) tank inside. I'm pretty convinced the chemical warfare from the leathers and some of the large mushrooms, plus insufficient circulation is why I could never keep some of the "weed" SPS (monti digis, caps, slimers, etc.) that seem to overrun other's systems. I did have a couple (1-2) acros survive, and one mille, but other than that every SPS I tried (basic ones, not exotics) slowly faded away over a matter of a couple months. My parameters aside from nitrates were OK, and I did run GFO and Carbon, but perhaps didn't change the carbon often enough. In the new tank my lesson learned will be no leathers or softies, no discosomas, some ricordea and zoos but no palys, and regular dosing plus GFO and carbon reactors. I'm optomistic this will result in a better success rate with SPS, but we'll have to see. Hang in there and try a few things; we'll get it figured out!