any one else have problem keeping fish

If they are all dying overnight did something happen in your house? Maybe someone was cleaning with some funky cleaners that get in the air or something?

Is the tank in a well-ventilated room so the water gets enough oxygen?

Maybe the door gets shut tight once a while and if the air is off it gets no new air or something crazy like that?

If your food kept frozen or sealed up well so it can't spoil?

Do you work with chemicals regularly that may be introduced into the tank on your hands if you accidentally forget to wash and rinse them well?

Just trying to throw out some out of the box ideas. Different things affect different organisms differently so just because your corals seem fine doesn't mean something isn't getting into the tank and killing your fish.

It isn't normal for batches of fish to die overnight regularly for no apparent reason.

For example maybe it's something weird like Otty ran into with his fireplace. Thankfully it didn't kill anything I don't think, but sometimes you need to look outside the tank to find the problem.
http://www.3reef.com/forums/water-chemistry/ph-co2-ventless-fireplace-have-common-trouble-43959.html

 

well it is really tuff to say what it is or was. no weird chems on hands from work cause it happend during the day and any poison would have killed coral too. food frozen and in cube form and didn't kill anything in other tank. I feed both at the same time. I truly don't know. if there was a o2 drop I would have never known. Only thing I could think of is fish died and temporaly raised the nitrates and killed other fish. If it happened in the morning and didn't come home from work maybe the raise would throw other fish in shock.