I have had my 20 gallon tank for about 6 months now and have 3 dwarf puffers and 3 Otto catfish. There are about 8 real plants and plenty of hiding places. I have been getting a lot of brown algae and the ottos only seems to clean waste from the bottom. They don't touch the glass or rock decoration in the tank. Is there another type of algae cleaner I could add to clean the walls and decor? Any suggestions would help. Thanks.