Try this: take a 16 oz plastic water bottle. Cut the top off about 1/3 of the way down. Insert the top half, small end first, into the bottom of the bottle. Then put an algae wafer, or whatever they like to eat in it and let it sit overnite on the bottom of your tank. It may take a day or 2, so don't feed them in the meantime. Eventually, they will venturein. Once in, they can;t get out. Kinda like a lobster trap. I use this method to catch pleco fry all the time, and it works great. Good luck.