huge gsp coral rotting away

[Liverocknroll]

I have a 90 gallon that came with a pretty big green star polyp coral that looks beautiful but for the past month or two it has not come out, its rotting, and it has some algae on it. The coral looks like holes are appearing in it and big parts are just falling off. It is partially coming out now as in I can see a few green tips from the very top of it. The tank has 0 Nitrates .11 phosphate and 1.23 salinity calcium is also 420. For the past 2 months the tank has also been fallow due to a ich break out. I have recently re added the blue tang and a clownfish. I suspect it is my hermit crabs eating away at this coral because in the morning I see them crawling off of it. The coral is attached to a live rock that is double arched by the way. I would love to know what you think is wrong wit my gsp coral and how I can fix the problem.

[acabgd]

Originally Posted by Liverocknroll

I have a 90 gallon that came with a pretty big green star polyp coral that looks beautiful but for the past month or two it has not come out, its rotting, and it has some algae on it. The coral looks like holes are appearing in it and big parts are just falling off. It is partially coming out now as in I can see a few green tips from the very top of it. The tank has 0 Nitrates .11 phosphate and 1.23 salinity calcium is also 420. For the past 2 months the tank has also been fallow due to a ich break out. I have recently re added the blue tang and a clownfish. I suspect it is my hermit crabs eating away at this coral because in the morning I see them crawling off of it. The coral is attached to a live rock that is double arched by the way. I would love to know what you think is wrong wit my gsp coral and how I can fix the problem.

Salinity is probably 1.023 and not 1.23 as you wrote. This is a bit on thw low side but no big deal. Phosphate is really high and you would need to bring it down. What is your alkalinity and how do you keep it in check? What lights do you use?