There is, what you will have to do is find some type of container that is big enough and tall enough usually one of those plastic large soup containers you get from a Chinese restaurant, place a piece of egg crate on top of the container, place the shell on the egg crate and when the fish swim out of the shell they will go to the bottom of the tank near the substrate, this could take a while but they will not be able to go back into a shell, i have used this method and it works..
If you do not know what egg crate is google the term its basically light diffuser and is available at home depot pretty cheap and you can cut a section to fit your needs..