HELP. Corals bleaching out

[scbasser5]

I have been out of town for several days but have had family watching tank. When I returned I had three SPS corals bleach out totally and a fourth that doesnt look so good.

I have checked the parameters and all appears good. I have done on 10% water change and plan another tomorrow.

I know this is not much info but I would appreciate any suggestions of what to check.

Thanks

 

[Serioussnaps]

swings in temperature, alkalinity, ph and salinity can do this....

did anything die in the tank like fish or something...??

did the lights go off for an extended period of time???

 

[scbasser5]

Alk went down for a couple of days and the lights were not as constant as when I watch them, LOL.