Undergravel Filter

Definition: An undergravel filter is a type of aquarium filter placed beneath the substrate. It relies on water movement through the substrate to provide biological filtration.

Function in the Aquarium: Undergravel filters promote biological filtration by creating water flow through the substrate, allowing beneficial bacteria to colonize and break down organic waste. While less common in modern aquarium setups, undergravel filters can be effective when properly maintained and complemented by other filtration methods.