Does it look like this? Columnaris Columnaris (Flexibacter columnaris) Synonyms:
Cotton-wool, Mouth Fungus, Flexibacter Symptoms:
White mouth with tiny filaments, white areas near edge of scales, clamped fins, fins start to rot in the later stage, fish struggles and sways near the surface Causes:
This is bacterial infection which is very common in the aquaria and is very contagious. Immediate action is needed to contain it before it spreads to other fish. Treatment:
Broad spectrum antibiotics, Sera Baktopur, Binox, Maracyn I & II, Kanacyn, Terramycin, Acriflavine, Furan, Copper Sulfate Flexibacter columnaris
thrives very well in warm waters therefore it is necessary to gradually lower the temperature to prevent it from progressing. Pictures retrieved from Sera guide by Dieter Untergasser for reference purposes.