So from reading other posts here I guess my red cap oranda has tail rot. He always had the most beautiful flowing tail until one morning I came downstairs and found him stuck to the inflow of the filter, with his tail gone. He's been 'cap heavy' for some months, not that he ever swam totally level in the nearly 2 years I've had him now. If it is a him. Whatever. He's only a couple inches long, in a 7 gallon tank with a comet and a fantail, all about the same size, with a box filter and relatively frequent water changes. I have a freshwater test kit and I've never had the water show any problems. However, I have recently started using an alga destroyer, the kind that's safe for plants, since the tank gets natural light and grows a lot of algae otherwise.

Anyway Mr. Red Cap has been slow and clumsy for a few months and he doesn't move fast enough to eat the regular goldfish food pellets the others eat so I add things like floating fairy moss for him to eat, or bits of dried tubifex worms, and there's a plant suspended in the water that he's eaten all the roots off of plus he goes through the gravel to get the pellets (grains really) that the others miss. Then the filter accident. I guess his tail was sucked off in bits by the filter but it would have had to be rotting to do that I would think, plus something really wrong with him to get stuck in the first place. I've had fish get stuck in the filter before and they didn't lose body parts like that. They died but they werent' pulled to pieces. So now I have him in a separate 2g bowl and I drop goldfish pellets right in front of him and he eats those with good appetite but otherwise he doesn't move, just sits on the bottom with his head down. The stump where the tail was looks sound and healthy, it doesn't look infected.

What's the prognosis here? should I treat him for tail rot, or is he dying anyway if he's weak enough to get stuck in the filter? If he needs treatment for tail rot, what about the other two fish, should I treat that tank too? they both seem perfectly healthy so far. They do get salt in their tank tho it's hard to measure out salt for such a small tank so I always err on the low side. And will he grow his tail back?