I just used the 2 liter bottle to catch my problem fish, it was a large, quick damsel. I took a few tries, but finally got him. I think I caught most of the other fish a few times first, especially my bird wrasse, he's not a very bright fish, on the other hand he was the only one getting fed and he probably figured if I let him out the first time, I probably would everytime. Pretty smart fish actually! Good luck.