I just set up a 100 gallon hexagonal tank a few months ago. I have 3 tiny oscars and a jack dempsey. Maybe about 3 inches in length each. So far they don't seem to be trying to kill each other. Also have a giant pleco (about 10 inches)

The pleco is not doing his job! I have one little live plant at the very bottom and I thought the roots were just growing like crazy! Took a closer look and nope it's fish poop. Just sitting there covering a solid half of the tank bottom. Ick!

Can I put another type of fish in there to help get rid of this? Petsmart mentioned a cat fish when I was first setting up the tank but I'm skeptical it wouldn't get eaten.

Maybe something to move the water around to help the filter catch it?

The pleco seems to love the piece of wood that I put in there so I think he's not hungry enough to keep the tank clean anymore.

What should I do? Any suggestions would be greatly appreciated