I was trying to catch a dragon goby from my tank and IMO
the bottle trap is useless.
This is the trap I made that ended weeks of being out smarted by a fish lol.
Take a piece of pvc
pipe and on one end use an elastic band to hold on a piece of saran wrap(if you use a pvc
cap its too dark and they won't go in). Put food in the open end all the way against the saran wrap so they have to go all the way in to get it. When they go in simply lift it up so the open end is up and the saran wrap end is on your sandbed. Fish don't know that they can just swim up and out so don't panic he won't get out. As you lift it out hold the saran wrap on or the pressure from the water will pop it off and you start all over(learned that the hard way lol). Then, you celebrate because you are the superior species hahaha good luck