OMG......

[Zoodiver]

Like mentioned before you should top off with freshwater, not sure what happened, sorry for your loss. SW tanks should never be allowed to drop to the point where they are an "eye-sore" however. You should have been keeping up with maitenence. With corals, water temp DOES mater. I top off 1g per day with aquarium temperature TAP WATER. Hope I didnt step on any toes.

Along with this, I'm going to go out on a limb and say something else was majorly wrong in the tank, and the topping off just pushed it over the limit.

I top off marine tanks with city water all the time. Unless it was REALLY low and chilled water going in - there wouldn't be enough swing (temp or salinity) to kill off things that fast. You'd need something like a 30% FW addition to get those kind of results.

 

[FLESHY]

Agreed. Remember in wisco the water comes out of my well here at around 47F...so yea. Some precautions need to be taken.

I think some of us didnt understand you were mid water change though. Hope everything is well now.

 

[Twixy]

Are you using tap water or RO?
I know some parts of the uk the water can be pretty much useless for anthing aquatics.