What's wrong with my Frog?

[mpmistr]

Probably a bad choice of words on my part. The filter media is a cartridge and its inside a filter that hangs on the back of the tank. A Whisper 10-30i, to be exact. The plecos are in a separate tank. I do, however, have six tetras (1 rosy, 3 white skirt, and 2 red serpae) that also inhabit the tank the frog is in, and they've never bothered each other.

Whispers are fine, I've used them in the past. I think the tetras may be nipping this frog, but it's just a hunch. Tetras are pretty nippy fish aren't they? There's a good chance it just happens when you're not watching.

If it's not the fish nipping, it's a water quality issue. Have you considered just getting a 20 gallon for this frog and keep it alone?