We brought home 2 new 1.5 inch fantails and put them in a 7.5 gallon we purchased to be their quarantine tank. When I set the tank up I put in part of the filter fabric from Marie's established tank in the new tank's filter, plus some of her rocks and one of her silk plants in the tank, so there would be some healthy bacteria at least.

That was on Monday. This morning (Wednesday), one of the little fish seemed listless and weak--he was kind of riding the current in the tank a bit. I lowered the flow on the filter to make the current slower, did a 50% water change and added 1 tablespoon of aquarium salt.

He doesn't seem any better, or any worse, but this afternoon I noticed his tail is significantly eroded, which I hadn't noticed before, although that may have been because until he seemed ill I didn't look all that closely at his fins, which are white/transparent anyway because he is a white fish. His lower fin looks clamped, and he is breathing heavily, too, and staying near the bottom of the tank.

I am afraid of using medication, as I haven't used it before. So I plan to continue with the water changes in hopes that will allow him to recuperate. I also thought maybe I should add an airstone to increase the oxygen in the water, especially since it is so warm now.

Do you think this is a good idea, and how long should I give the water changes and the airstone to help him before I consider meds? Thanks.

Unfortunately, the little fantail died. I brought home the airstone and set it up, and he was resting in a plant at the time but died soon after. The fins on the sole remaining fish look perfect, so I am hoping that frequent the water changes will keep her healthy for the rest of the quarantine period.

I have another question about the current in the tank but I will post it seperately so the heading will be accurate.

I'm sorry about the new fish. I suspect he wasn't healthy when you got him. I would have treated him with antibiotics. If ever there's a time to risk medication, it's with new fish (to which you're not attached) who are in quarantine. That's the point of quarantine. You may want to use at least the aquarium salt and MelaFix (all natural antibiotic) on the remaining fantail. If the other one had fin and tail rot, that bacteria is pretty contagious (but may be ubiquitous which means always present and only attacks when a fish is weak).