Penn-Plax Tank Dividers instantly convert one aquarium into two. Quick and easy to install, these polymer screen dividers are great for creating breeding tanks or for separating rough fish. The perforated screen allow unrestricted circulation and filtration and even heat flow. Available in four different sizes to fit most tanks up to 55 gallons in size, these dividers can be trimmed to fit your tank perfectly. A convenient and efficient way to protect your fish without major modifications to your tank.