Recently, because of new flooring, I emptied all the water from my 75 gallon tank. Then, of course I put it back for a day then emptied it all out again and the refilled again. A lot of sediment was disturbed and my 13 year old tang died. (Can't believe they are $500 now). But more disturbing is my large polyp colony I've grown for 30 years is diseased, partially closed all the time and sickly. Also my anemone I need for the safety of my calico clown pair is not well. I'm afraid that obsessing may do more harm than good. Are there any high probability proven cures? I also got a concomitant algae issue that I'm managing. All the parameters are literally perfect from Ph to specific gravity, temperature, etc. No phosphates or nitrates and I've done 4 water changes. I'm sure it's stress and disease. And perhaps my not feeding the anemone until lately. I know antibiotics are an option but I'm totally ignorant about that. Thanks very much for anything useful. I'm sort of in the hope and do no harm stage.