I love keeping animals, but I hate when they're struggling and I don't know how to help. Just done the usual check I do every few days on my tank, peering around everything to look for anything out of the ordinary. Found a cardinal tetra dead at a filter intake, been gone for a couple of days from the condition of it. Also noticed one more cardinal having swim bladder issues (active enough, but a good 45 degrees off true). The rest of the cardinal shoal, and the rest of the tank contents seem absolutely fine. Reckon it's just "one of those things", or something else? I'd dose melafix, but I've got Honey Gourami's in there, and I know the two don't always mix well. Amanos, Oto's (sensitive in the extreme!), botia striata, galaxy rasbora, white tail mountain minnows, all 100% happy. Any pre-emptive action to take, or just a watching brief?