Please dont! Your Plecostomus are Common Plecos, and will get to eventual lengths of 2 feet! Giving them to students will create misinformation and bad lives for the fish. Common plecos need gigantic tanks!Mystery Solved! I placed the tank structure prop outside the tank and sifted the gravel. When I lifted it, there it was - the second Pleco (and some fry). Time to gift them to the students.
Thanks everybody.