After you've done up your DIY fish trap,
make space on your sand bed to place it there..
before you do that,
throw a frozen cube of your fish favourites..
eg. henry's food, mysis, cyclopeeze..
first ones to go in would most likely be your shrimps or snails..
depending on how greedy your fish is,
they should be in soon.
now all you need to do is sit back, relax and wait for your fish to enter..
once the your targeted fish enters the trap,
reach down, turn the trap vertically up..
they'll go "crazy" in the trap,
do not worry as chances of them swimming out through that same hole is not very high..
things to note: ensure that the mouth of the trap is not too big, just nice for the fish to enter