My sis in law has a large koi pond. The other day she said she thought she had a crayfish in her pond eating plants and terrorizing fish. Anyway, today she captured it and brought it to my house. Right now it is in a small 5 gallon aquarium in my boys room that only had a mystery snail and ghost shrimp in it. I removed the mystery snail but left the shrimp. The crayfish is about 3 inches long. I don't know anything about them but I am assuming a 5 gallon tank is too small to keep him in. I have a planted ten gallon with a very old betta fish in it but If I switch the betta to the 5 gallon and put the cray in the 10 gallon will he eat my plants? My sisinlaw is blaming him for plant destruction in her pond. My other tanks are a 55 gallon community tank that is full and a 10 gallon dwarf puffer tank. Should I just take him and put him in the large public pond down the road. Geez, I can't believe I am worrying about a crayfish but he is kind of neat looking.