That maroon colored alage is actually a photosynthetic bacteria called Cyano. It thrives in poor water conditions. It can release a toxin that can kill fish/inverts if it gets out of hand. I'd suggest doing at least a 50% water change and sucking out as much cyano as possible because it's a potentially serious problem. I used to have hardcore cyano problems then I slapped a good skimmer on the tank and the cyano pretty much disappeared.phensway said:why do you say its time for a water change?? is it because of that maroon color algae???