Nice trap You've got there =)
I made one myself also, a little more simple but it seems to work fine.
I cut of the top of a ½ a liter cola bottle and put the top back in the other way around.
Then I put in a shrimp through the hole and waited.
I had to catch a crayfish, with eluded me and hid for an eternity.
I bet if you use a bigger bottle, you can catch bigger fish =)