if you have Common Plecos then I doubt they are cleaning your tank. They are one of the last fish that I would suggest for that job. You probably just dont have an algae problem in the first place.QUOTE]
I've got common plecos that do a fantastic job on tanks that I've had MAJOR algae problems in. They do a very good job of keeping the tank clean, however they get very big and create an awful lot of waste.
In my 20G guppy tank I've got Hong Kong Plecos...at least that's what the LFS called them. They're really small...I didn't want something eating the babies cuz I want them to grow for Oscar "snacks". These are so cool looking, and I believe the max growth is around 2-3 inches. But like otos, you'd need to get a few. I've got 2 in the 20G and I'm thinking of getting a few more. They do eat the algae, but I'm going to need more to take care of the bulk of it. Afternoon sun shines in the room and algae is a bit of a problem here.
Good luck!