This just worked the other day to get a mean little domino out. I tried netting, cornering, all that....and just got mad. So here's what you do: Get an empty plastic pop bottle (16oz or so) and cut the top off where it starts to taper into the opening (about 3/4s up the bottle), cut the opening off so it's just large enough for the fish to get through, flip the lid inside the bottom of the bottle. Don't silicon it because you'll want to get the fish out, just make sure it's tight. Drop some food in there, place it sideways in the tank, and wait...It'll find it's way in. Good luck!