Plecos get huge-even in small tanks. I'm a firm believer in giving fish the most natural food available. I once saw a 22-inch pleco in a store in Florence, SC. When I asked the owner what he fed the fish, he said "zuccini." Ever since I have fed my plecos a piece of zuccini (large or small depending on the size of the fish) every two or three days. Just drop it in the tank and let it float. I love watching the fish latch on and feed upside down. Cut off the skin before feeding it smaller fish, but larger plecos will eat the whole thing. Other plant eaters in your tank will help with any remains. If you feed an appropriate amount, I think you'll find less waste that is also easier to remove from the tank. If your problem continues, try making a small depression in an inconspicuous location to collect the waste and spot siphon once a week.
"Whether you think you can or you think you can't, you're right." Henry Ford