Cloudy water and fish death

Only thing I've done is scooped out a dead fish. Something else I was thinking about that changed before this happened was the addition the filter sock I sometimes run to polish the water. Wonder if something could have been on it?
Just can't believe this thing can go from looking spectacular Friday to crap Saturday.

 

I see that your tank was reborn 5 months ago, is this the 180G tank? I had a bacteria bloom in my 150G, with patches of white fungus looking stuff growing all over the tank, usually where turf algae was growing. I ran erythromycin in my tank (after it was cleared of all livestock) for 4 weeks, scraped off all the algae in the tank, ran a UV filter to kill any free floating bacteria and ran my skimmer like mad cleaning it every 2 days. I would try running some antibacterial meds if it got down to desperation stage, stuff that is safe for reef anyway. I wish you the best of luck, I feel your pain on this.

 

Went home after class last night and the water was clear, fish were all fine, no excess skimmate. Went ahead and added some carbon for giggles. ORP was the highest it's ever been this morning. 435.

I did almost make a big mistake though. yesterday morning when I scooped out the naso I shut down my closed loop and one of my heaters. Well I forgot to turn this stuff back on before I went to work. 15 hours later I came home to the tank and the temp was 76, acros were all closed up. Figured it out quickly but it could have been bad.

Don't know. :-/

 

Your tank didn't like that it was 76? My fish and anemone seem to thrive at 76ish. If it gets to 78, the anemone deflates down to a nub, if it gets cooler than 75 the trunk is full but the tentacles get short. It's weird.

 

Tank always stays at 78-78.4. Everything seems to like it. Acros and cup coral didn't like the cooler water. Well it could have been the flow was way down as well. A mag 18 isn't really enough flow for a 180. Better than nothing thank Jesus.