Well I also use pvc pipe to target pellets into caves instead of putting my hands into the tank. I second the grow your own algae idea. If your fish are destroying veggies, growing your own might be a good idea. The plecos shouldn't have competition with that. You could also try something like seaweed. Wrap it into the inside of a pipe or cave to where he is the only one going on and scraping it up. I don't use seaweed and don't know how healthy it is, but I know others use it to supplement plecos
Also with the veggie idea, I personally add 2, 6 inch chunks for my tank. It's normally too much for any fish to completely steal but still gets completely eaten within 24 hours