Goldfish Fin Trouble

[RobLe]

About 10 days ago I noticed a section of missing tail fin with a red outline on my comet goldfish. Since he seemed to be otherwise perfectly healthy, I simply performed a 25% water change and added some salt to see how things progressed.

By the end of the week, prominent red veins appeared between the tail of the fish and the missing fin section. I performed a 50% water change and have now begun dosing the tank with Kanaplex under the assumption that it is an infection that seems to be getting worse. Since then, small veins have also appeared on the lower pelvic fins. As when I first noticed the issue, I still have seen no changes in behavior or appetite (or any other abnormalities anywhere else on the body).

I'm wondering if someone could help in identifying and providing any advice on his situation.

Current tank information:
Size - 55 gallons (cycled for 1 year now)
Ammonia - 0
Nitrites - 0
Nitrates - 20-40 ppm
pH - 7.6
Temp - 75 F / 23 C
Filtration - Fluval U4 (260 GPH) and smaller U2 (105 GPH)

Nothing new has been added or changed in the past two months, only change has been they've eaten almost all of their plants and I haven't replaced them yet.

 

[BBradbury]

Hello Rob...

Are you adding aquarium salt to the Goldfish tank water? If not, you definitely should be. Up to a tablespoon for every 5 gallons of replacement water. I add it to my Goldfish tanks and I would recommend it. If you keep aquatic plants, then you want to reduce the salt to a teaspoon in every 5 gallons of your replacement water. The tablespoon amount is for treating an infection and you don't need a lot if you're dosing for general fish health.

B