Interesting comments...
My plecos picked clean all the algae in their respective tanks within a week. I tried feeding algae wafers and they totally ignored them.
I feed my discus beef heart flake mix and freeze dried black worms. The plecos would just about attached to the FDBW, pushing out the discus during feeding time, and ate a steady supply of the flake food too. Only the largest pleco actually was bothering my adult discus. Clearly tried to attach to them. The discus more or less swam away and ignored the plecos attempts.
All the plecos had been growing fast in my tanks. Maybe a varied diet would have hepled.
Regardless, they're in a new home now.