Hi Caroline,

Have you tested the water with a freshwater test kit? What are water readings?

Fungus and bacterial infections will often develop when there’s a problem with water quality. So first, make sure water conditions are healthy if you haven’t done so already. I’d recommend at least testing for ammonia and pH. If you can, also test for nitrate and nitrite.

For the fungal infection, I recommend Methylene Blue. It’s gentle on sensitive fish and you can couple this with aquarium salt to help reduce stress. From my experience, Pimafix doesn’t treat all fungus infections so you may need to try an anti-fungal medication with different active ingredients.

Before treating the aquarium with another medication, you should change 40% of the water. After that, change 25% of the water for three more days. You want to remove as much of the old medication as you can before treating with another medication. Otherwise, you might over-stress your fish. The water changes will also help you get water conditions back under control if water quality caused the infection. I still recommend testing the water if you haven’t already done so.

You can also start treating the water with aquarium salt in the meantime as you complete each water change. Since salt doesn’t evaporate, only treat the water with aquarium salt after a water change (once you’ve treated the water initially).

Likely the fin rot will heal after your fish are no longer stressed from the fungal infection. But if it doesn’t, you should change the water daily for 4 – 6 days like you did before and treat the aquarium with an anti-bacterial medication. I personally recommend Maracyn-Two for bacteria. You might not need an additional medication for fin rot though, so treat the water for fungus first (unless the fin rot is real bad and fins are deteriorating to the base).

If fin rot is severe, you might want to medicate the aquarium with an anti-bacterial treatment first – if the fins deteriorate to the base, your fish won’t be able to grow them back.

Good luck! I hope your fish have a speedy recovery.