I've had this studfish for 15 months; was ca 3/4 grown when I caught it. Have fed it bloodworms all this time, served up in front of his nose. About 10 days ago just flat stopped eating. Seems fine other than that, though starting to lose mass. i changed out 1/4 or so of the water a few weeks ago, everyone in the tanks seems fine as ever--3 Bleeding Shiners, a Fantailed Darter, a Banded Sculpin and a Logperch. It might be eating a bit that I'm not seeing, but totally ignoring when I try to feed.
Any ideas what might be going on?