I have a 10 gallon with 2.8 watts of light (it is rather heavily planted) yet I get a lot of algae, especially films of algae on the larger leaf plants such as sword plants and java fern. It also grows on bushy plants. I just wipe it off but it occurs again. I'm not sure if I should get ottos though. I have 3 leopard cories, 1 skunk cory, and 1 male betta.