Tree Trunk Tropics provides instant landscaping for your aquarium. It is both a background and a biological filter and it provides a framework for adding landscape, such as wood and aquarium plants. Once set up, Tree Trunk Tropics will give an aquarium an immediate environmental feel, simulating a river’s edge bordered with trees and overhanging roots. You can add T-Rex Aquavine, Aqua Root, plants or other aquarium décor. Live aquatic plants can be anchored in the foam by making a small slit in the foam and inserting the roots or artificial plants can also be inserted in the foam. Tree Trunk Tropics is primarily recommended with smaller fish that have an adult size under 4 inches, aquatic frogs, tadpoles, newts, freshwater shrimp and planted aquaria. Because it consists of open-celled foam, Tree Trunk Tropics also provides a very effective aquarium biological filter when connected to an air pump (not included). Although Tree Trunk Tropics is designed to be connected to an air pump and function as a filter, it can also be used only as a background. It is pre-fitted with two lift tubes and air diffusers located at the top of each side. You can connect the filter units to airline tubing attached to an air pump. This will transform Tree Trunk Tropics into a high-surface, efficient biological filter. With regular water changes, this filter will be sufficient for maintaining up to 1 inch of small to medium-sized fish per gallon.  Tree Trunk Tropics 20 Gallon is 24" L x 4" D x 15" H