I have a ten gallon tank, been set up for approximately 4 months. I have 5 zebra danios and 1 sunburst molly in it right now. Aquaclear 20 filter, aerated, heated to 76-78 degrees. Live plants. 25% water changes every 4-5 days. Fish are all fed a mix of tropical flake medley and brine shrimp.
Last week the molly developed ich, so I treated the whole tank with rid ich+ and upped my water changes to 25% every other day. The ich was a little stubborn, so I had to treat for a full week and today is the first day that I definitely see no spots. I never saw spots on any of the danios, but left them in the tank while treating it to be safe.
All the fish seem to be fine and seemed to do OK with the treatment, but 1 of the danios is definitely sick. He got increasingly lethargic - I first noticed because he would just sit at the bottom of the tank while the others were playing at the surface. I wouldn't be able to find him until I used my net to poke around at the bottom because he would sit that still for that long. That was about 2 days ago.
Today he's been doing the same thing, only every once in a while he will swim to the surface like a maniac and flop around up there. He doesn't really seem to be "swimming" as much as chaotically flopping and zig-zagging and jerking. His breathing is pretty heavy, but otherwise I don't really see any sign of "disease" on his scales or body.
What is wrong with him? It doesn't look like a swim bladder thing, as he can definitely keep himself balancing and sitting on the gravel for a long period of time.
Does it sound like something he might recover from? I moved him into an isolation tank (I do treat the water with Jungle conditioner) with all fresh water, but I'm not sure what else I could do. The isolation tank so far hasn't made a difference.