Can 2 plecostomus be in the same tank together?

It depends on the size of the tank and the species of pleco. Some species of pleco are more territorial than others, and may not tolerate another pleco in their territory. In general, it is best to keep only one pleco per tank, unless the tank is very large (over 100 gallons) and there are plenty of hiding places for the plecos to avoid each other.