Additional aquatic plants may be necessary as crayfish like to eat them. Another alternative is purchases large leafy greens from your grocery store such as swiss chard. Crayfish will hide under it as well as eat it.

If you cannot obtain crayfish to use in Investigation 3, teach the alternative Investigation 3 "Meet the Hissing Cockroach" and obtain Madagascar hissing cockroaches instead. This alternative investigation can be found in the Resources by Investigation section for Structures of Life listed under Investigation 3. The LOC from Delta Education provides 8 cockroaches.