My brother and i have been debating this. I like all the glass to be cleaned regularly to make sure nothing is growing one the glass. so this has sparked a debate about whether if algae grows on the back of the tank is good or bad. He argues that it is good and does not make a difference because algae occure naturally and in the wild. I believe that it may not be harmful is just an eye sore and i really would never want it on my tank. Could anyone tell me is it good or bad or really just doesnt matter.