i have never heard of any fish eating other fish poop. are you sure????

plecos and goldfish are the POOP KINGS of the fish world... so... if your tank is a little overstocked... as a 90 gallon would be with two oscars, i would consider not bothering with one. perhaps a bristlenose IF you have an algae problem but honestly, most plecos only eat algae when they are small and need to be fed algae pellets when they grow up (cause they get fat and lazy LOL)