The bump is red, it is about a centimeter,it is more bulging out then just a bump and it is kinda rocky. The tank is a 10 gal with one gold gourami a paradise fish,a glass fish, a cory cat, and the gourami. It has live plants in it with a aquaclear mini as a filter and a heater that stays between 76 and 78. I feed the fish and it acts normal. P.S this has happened before and it went away so let us see what happens.