Instead of simply telling him his tank size is wrong how about answering his question?
It sounds like you have quiet the cleaner on your hands! I have heard ofnit happening before so I think it is kinda normal. Plecos are very very shy when first introduced into a new tank.
Now the above poster is right. Your tank is about 15 times to small for him
I recomend either getting a bigger tank once he hits 3-4 inches or taking him back and getting otocinclus