Duetto multi-filter is an internal filter that is ideal for reptile tanks as well as aquariums because of its small size and versatility. The separate components for mechanical, chemical, and biological filtration permit easy replacement and cleaning of the chemical and mechanical filter without disturbing the biological filter. Duetto multi-filter includes an adjustable aeration feature that mixes filtered air with pumped water to improve oxygen /carbon dioxide exchange. Because it has two different output adapters and the ability to be positioned either vertically or horizontally within the tank, the Duetto multi-filter easily adapts to many different applications and configurations.