Strange Regular Fish Deaths

[Ozzy Ozborne]

The platie that looked ill is now a gonner ...........
Found him dead this morning!
last night he was either gasping at the top of the tank for air...........or at the bottom either quiet or breathing very heavy with his mouth constantly opening and closing.Anybody ideas what this is...............is ita lack of oxygen in the tank?

I have put the filter outlet pipe up vertical to agitate the surface,put in a powerhead (Hydro Koralia 2) and also given a dose of general tonic (Interpret)

All water tests are still fine,and all the other fish are looking ok.
Does all this make sense and am i doing the correct things?

Thanks

 

[OldMan47]

You are certainly doing all that I would be except for the general tonic. I stay away from all chemicals except dechlorinator. The other thing I always do when I can't figure out what is harming my fish is to ignore the chemistry set and do a water change or even two to make sure there is nothing in the water harming the fish. The chemical testing we do only tests for the most common 2 poisons but there are hundreds of possible poisons in your water. One of the worst is chlorine so double dose the new water that you add just in case the local authorities have decided to increase chlorination as a precautionary measure. It happens so often around here that I double dose all my new water just to be on the safe side.

 

[meguro]

If chlorine was a problem why is his bacteria colony seemingly intact? (as another poster also pointed out)

 

[OldMan47]

It would take more chlorine to kill your filter bacteria than it would to kill your fish. Once established, the filter bacteria are actually fairly tough to kill. We avoid all kinds of things while trying to get them started but once they are going they are tenacious.