2 words Otto Cats...they are amazing at cleaning algae, and they are small, about 1/2 - 3/4 inch in length, they stay small. They are peaceful fish and when there is no algae left they will eat cucumber and zuccini, algea wafers etc.... cory cats are good to eat left over food off the bottom but not algea really. you could get 1-2 otto's with out really maxing out your tank limit...cory's can get fairly big and should be kept in at least pairs. you could combo 1 otto & 2 cory's if you want, but be sure the cory's are small. I have 2 otto's in my 10 gallon and they keep it sparkling clean!!! Plus they are really really cute and fun to watch eat.