I'm thinking of buying a crayfish from the petstore but I'm not 100% sure about The Crayfish are pretty cheap ($1.99) but I heard they eat anything (including Goldfish) and I don't want a hostile enviorment in my tank. My 6th grade scince teacher had a crayfish in her goldfish tank

Hello

crayfish shouldnt be put with fish as thats their natural prey, and with goldies sometimes sleeping on the bottom then they will easily get attacked.
if you want one then i would suggest a 2 foot tank all to itself.

Are you sure it wasn't the other way around? Having goldfish in a crayfish tank?

They'll definitely attack your goldfish at some point, so better pass on them unless you want a separate tank.

yeah, i put a crwfish in my goldfish tank and they were commons and were pretty fast, the crawfish still killed one of them though. i removed it as soon as i saw a dead fish.

Crayfish will eat anything. Even each other in time. They are best kept alone.