My beutiful chiclid tank suffered a huge fish die off this morning. I lost 8 nice fish. I removed the other fish and put them in another tank. Has anyone had this happen? What did I do wrong? 

Sorry. I know that is heart breaking to find. Could have been ammonia poisoning. Basically,too much fish pee in the tank. How big is your tank and when was your last water change. the same happened t me only there were a million guppies in the tank. Def ammonia poisoning. There is a test for it. 

I have a 75 gallon tank. It really stinks, so maybe it was the ammonia.My last water change was a week ago, 1/3 of the tank. 

I have a 75 gallon tank. It really stinks, so maybe it was the ammonia.My last water change was a week ago, 1/3 of the tank. 

Were the 9 fish large? The rule is 1" of fish per gallon. Sometimes that makes a difference. Sorry. You can test the water to be sure. I always did half water changes to my 55 gal. 

If you use tap water it needs to be treated to remove chlorine. I always use RO/DI water and keep a 25 gallon bucket made up for water changes. A 10% to 15% water change weekly should be okay.