I have two Common Plecostomus, they are about 6 or 7 years old, one has recently worried me as it has burrowed and will only come out when I drop food in. It has made it's home in a castlo and created a pocket in the gravel. they are both fairly large about 7-8 inches and kept in my 50 gallon tank with my gold fish who all get along great now that my larg goldfih has passed on(about 15 inches wouldn't even fit in a produce bag certanly to big for a bureal at sea, aka flush.....) Both my Common Plecostomus get a long fine with each other and the gold fish could they be breeding? the hole it has excavated is to deep for me to see into with it constantly on top of it. have no clue as to what sex they are. in the years i have had them it has never acted like this. it is not agressive to the other one at all. Please respond.

eventually you will need to seperate them because adult plecos cant tolerate each other. I doubt they are breeding because they would need an EXTREMLY large tank. You shouldnt keep them with large gold fish because the plecos will suck on them.

My 14" pleco loves to dig pits in the gravel. Common plecos rarely breed in captivity. Breeding size is a foot or more so yours are still a bit young anyway. I do not know of a single case of a "common" pleco breeding in an aquarium except I think for one in a 200 gallon tank in Europe once. I guess it's possible that you don't have a "common" pleco but perhaps another less common fancy sort of pleco, and they are interested in spawning. Keep an eye out that the plecos don't bother the goldfish.