FISH DYING AND BREATHING HEAVY

[reefcat]

Before I took the powerheads out they were like that. And thats when this all happened, salinity is 0.024. Im scared to put the powerheads back in unless i know theyre clean

[Lampshade]

The powerheads would have to be dipped in something pretty nasty to cause that much chaos. Diluted to a full tank system, it would have to be something VERY strong to cause something like this. Try looking at other causes, what are your nitrates at? nitrates will strip oxygen from the water faster than anything if they get out of control. You said your skimmer is not hooked up? what are you using for filtration currently? it that leeching nitrates back to the tank?

[reefcat]

Nitrates are 0, I just have a fluval 205 running like i have for the past 2 years and I was just gunna install the skimmer and the powerheads, all this happened in one night after i installed the 2 powerheads. I clean the filter alot so it cant the putting nitrates in there.