Try removing some eggs with a turkey baster. Take these egg and add them to a Tupperware 6x6x3. Fill with tank water. Float on top of tank and add a drop or 2 of meth/blue. Add a bubbler on low. Change water at least twice a day replacing the meth/blue. If after 3-4 days they become wigglers they are a confirmed pair. If they don’t they are not.