I came home from work today to find that my 2yr old Severum and a Angelfish had died, in my 55g.
My first impression was that during my last weekend tank cleaning of a 1/2 water change, and filter insert changes, that something had gone horribly wrong. I use Prime and Stress Zyme with every water change and test the water after every service. I've done this every two weeks since I set the tank up without fail.
The first thing I did was check my parameters, and they were right on. Then I really started looking inside the tank. I found what I think was the cause. There were three small pieces of ceiling acoustic attached to the filter inlet.
This tank has been in the exact location for 2yrs and I've never had a problem. I always keep the top cover lids closed, unless I'm feeding. I now realize, that no matter how small something is, that it "CAN" get in the tank and your fish "WILL" think it's food. I have installed non-metallic screening material over the exposed areas around the filter.
It's a very hard lesson to swallow. Even fish can become a member of your family. They can be replaced but their personality's cannot.
Thanks for letting me share, and maybe someone will read this and cover their openings and we can save a fish or two.