I have a 12 gallon JBJ cube and have turned the back middle chamber into a fuge growing chaeto. I recently made up a home made light fixture that holds a standard light bulb onto the back of the tank and light's it up from the outside in. I recently went to trim out the excess and noticed that everything that faced the bulb had turned brown. Is that from too much lighting? Should I just find a dimmer bulb? Thanks.