Hello, I started my aquarium several months ago and I currently have 5 fish living in the tank. 3 Platys which seem to be doing fine, and 2 cherry barbs, one male and one female. Recently, the cherry barbs have become very lethargic and have not eaten very much. Subsequently, there seems to be some sort of growth coming from their anus. The area around the anal fin is dark in color and there appear to be red pointy protrusions from the anus. The fish are slow to move with periodic bursts of erratic movement. Their fins are for the most part clamped and they spend most of their time floating in the same spot motionless. Whatever is affecting them does not seem to be having any effect on the Platys as of yet. But I hope to resolve this before it does spread. The water conditions are all normal and the water is clean. There is some sort of black hairlike fungus or algae growing on the wood in the tank. It is cauliflower-like in appearance and occasionally grows to be very large. The fish do not seem to eat it though. Please if there is any help you can offer that would be great. If more info is needed I will try to provide it.