[header] How to cure betta fish diseases [title] Notice if your fish's fins look clumpy or your fish is not as active as he usually is. [step] Your betta may also have a paler hue than normal and white or cotton-like patches on his body. These are all signs of a fungal infection. 
Fungus can grow in tanks that are not treated with salt and aquarisol once the tank water is added. [substeps] The fungus can spread quickly from one infected fish to the other fish in the tank so it should be treated right away.