Goldfish Fins Healing. One of the most dangerous causes of goldfish scales turning black or goldfish fins turning black is that your fish are suffering from ammonia poisoning. If fish are paired with aggressive or incompatible species, they will most likely develop fin rot.

Once the goldfish are dipped, the fins and slime coat get very ratty looking. High concentrations of ammonia and nitrates in aquarium water can inhibit fin healing and regrowth. The goldfish will look normal in.

Betta Fins Torn. Fin rot is a progressive disease that eats away at and dissolves the delicate tissues of your betta’s fins and tail. Damaged fins can lead to fin rot.

By suki, 6 years ago on general freshwater questions. Use a vacuum to clean gravel from old food, debris and feces. Fin rot usually takes some time to work down to the body of the fish.