feed them real good before you go and make sure the crayfish eats. They will be fine or use a feeder block; a small one. I have used those and they work well. I doubt the crayfish will concume all the fish in 3 days especially if you feed him. My crayfish only actually eat about once every week or so. Now if it were a blue crab ur fish would be goners, That I know from experience. I lost 3 pompano 2 trout 2 redfish and a flounder to 1 bluecrab in about 7 hr period.