Have lost 3 fish in QT

[jlbfish]

2 pygmy cories and 1 Flame tetra. The water parameters have been ok. Ammonia has never gotten above .5 Nitrites are 0. Sadly Nitrates are 0 (my media was killed wtih the last ISO group). I have been doing daily 50% water changes and testing daily. They have been here for almost one week.

I though the Red Eye Tetras that were in the tank had ICH so I moved them into their own 10 gallon and they are fine so far.

There may be nothing wrong. Not sure if I should do a Pimafix/Melafix combo?

The first Cory Hasbrosus died the morning after I brought them home. He was very inactive to begin with.

The second I found tonight stuck in the filter intake. I have since put a sponge over it I think he got stuck but am not sure.

There is a flame tetra that was breathing rapidly and is getting weak. I have moved him into his own bucket for now assume he is done for. He was happy to be sucked onto the filter sponge and stay there.

There are no signs of illness on these fish visible or that I can see under a microscope. I of course haven't checked the flame tetra yet. He is older than the others but I am not sure that would be the reason.

Any advice? Or should I just leave well enough alone for now?

Attached is all I could see in the flame tetra. No fin rot. Does it look like anything to anyone?

 

[jlbfish]

Any opinions on this? I think I am writing it off to bad luck. Nitrates finally started showing in my seeded media. As far as I knew below .5 ammonia wouldn't cause death with daily 50% water changes.

Thanks!