fiberglass vs pleco

most plecs are pretty poor at eating algae, cept commons, ancistrus sp. and a couple of others. a lot of the plecos have teeth too, so the chance of trying to digest i would say would be high, but i dunno if it would be bad for it. i cant imagine it would be good, but...
id find another way, even one giant royal wouldnt keep a tank that size particularly clean

I had the revese problem...my plecos would find a thin spot in the fiberglassing (wood tanks with fiberglass lining) that are not visible to the naked eye and concentrate on that spot until they had gone right thru it and caused a leak. Twice in one tank and three times in another. Escape plan? maybe...

I highly doubt they will digest it. I have a L114 that made it's styrofoam/cement cave larger by chewing out the styro foam. Still alive and well. Only problem is the styrofoam mess it has made.

my 20" comon still hasnt put a hole in my liner yet

Mine was a 14in common. Don't know where the remnants went, but I always watched where he stayed from then on.

well a lot of plecos eat and digest wood, and i know plecos have digested homemade caves made from styrofoam and died (unsuprisingly) so its something i would be at least cautious about