Since that minnow trap is made of metal, wouldn't it contaminate the saltwater by being left in there? Make your own trap out of a 2 liter soda bottle. I just made one out of a
16 ounce soda bottle and it works. Cut the very top off of the bottle and discard it, although you could leave yours on because of the small diameter of the snake. Then cut the top section of the bottle off, right below where it starts to taper. Then take this section and place it inside the lower half of the bottle, with the taper facing inward. You may want to glue it in place but it will fit snugly. Place some bait in there to attract the snake. When the snake/fish swims into the bottle, the taper directs him into it but when he tries to swim out, most of the time it will swim along the bottom or top of the bottle and cant find the opening. Make sure when you put the bottle in the tank, that you lay it on its side. I am at work now but when I get home I willtry to take a picture of it so you get a better idea of what I mean. Anyway, good luck in catching it.