I like the cut off soda bottle when done with care!
Basic idea is to cut off the top that tapers on many bottles, reverse it into the remaining section. Add a touch of super glue if the fit is not snug enough to hold it. Fish go in and can't figure to go out the same way! Make lots of holds for plenty of water to move through. This is where the care comes in. If not enough holds to allow for plenty of water, too many fish can get in and die! The holes need to be a s large and as many as practical but also small enough that the target fish can't get out? A string tied to the top and left where you can pull it out and then some favored food make it complete. When you want to release the fish, pop the glue joint.
You can avoid catching a lot of the wrong fish if you add a divider in the tank to separate them.
Last edited by PlantedRich; 11-20-2017 at 01:01 AM.
Reason: added info