To be honest, if my mom was hounding me to get a pleco for my 20 gallon I'd just tell her that they are very agressive and will eat other fish. It isn't true, plecos usually won't eat other fish, but if its the only way...
You could tell her about the size, and the recommend 3 oto cats. They are still "sucker fish" that will eat some algae, but only get to around 2 inches.
Or you could point out that the cory cats will eat the extra food that falls to the bottom because they are bottom dwellers.
You could tell her about the size, and the recommend 3 oto cats. They are still "sucker fish" that will eat some algae, but only get to around 2 inches.
Or you could point out that the cory cats will eat the extra food that falls to the bottom because they are bottom dwellers.