So, as I feared, the Kanacyn wrecked the cycle in Otis' tank. This means I'm back to nightly aquarium water testing for the next four weeks.
The worst part is that Otis' sore has not gotten any better. In fact I think it's a little bit bigger than it was when I first treated him. So tonight I started a second round of Kanacyn. I figure, the cycle is already wrecked, so if I'm going to treat Otis a second time it might as well be now.
But if the second round of meds don't heal things up, I think I'm going to stop. Kanacyn is a pretty hardcore fish antibiotic; if it isn't doing the job I don't think it's likely that anything else will. There are other antibiotics I could try, and if Otis wasn't geriatric (for a fish) I probably would try. But at his age I just don't think I'd be buying him that much extra time.
Water parameters for Monday, May 17:
Ammonia - 0.50 ppm
Nitrites - 0.00 ppm
Nitrates - 10ppm (no retesting until appearance of nitrites)