Place Zoo Med‘s Hermit Crab In Your Hermit Crab‘s Aquarium For It To Grow Into The Same Way It Would Do In The Wild. Place these shells in your hermit crab s aquarium for it to grow into the same way it would do in the wild.. A great pet product. All items are brand new never worn and never used. Growth' Shells are the perfect natural shell to accommodate your pets changing size! Give your habitat and Hermit Crab some style with Zoo Med's variety of Decorative shells, ranging from: Fancy, Neon, Glow in the Dark, Decorative, and Patriotic!