good morning all, my name is Joe and I am 4 months new to this hobby. i have a problem in regards to my tank has had a few cycles and my water is tested weekly in addition to proper water changes and my salinity is great.....but I have lost three fish thus far (Ihave 5 fish) in a 75 gallon tank with a 55 sump? any ideas what is going on when all my levels are good? thanks again!