Hey bettanova2. That is a Red swamp Crayfish and it can grow up to 6 inches long... so it is not suitable for a tank under 20 gallons...
i suggest you put him in a larger tank or he will be stressed and will not color up nicely. I have done extensive research on them since i too have got one recently and they are truly delightful usually
i keep mine in a pond where he eats dead plant matter along with any insects or worms available. sometimes i feed him a raw shrimp which he takes happily.
They help keep your aquarium clean and look a wonderful when they are fully colored up; a deep red and sometimes with a blue sheen on the pincers