Lily pipe

A lily pipe is a piece of shaped glassware, usually named for its flared, lily-like outflow end, used in place of standard plastic fittings on a canister filter's inflow and outflow tubing. Aquascapers use them mainly for appearance, since clear glass is far less visible inside a planted tank than the black or green plastic fittings that ship with most filters.

Beyond looks, a lily pipe's shape also affects flow, with a wide, flared outflow spreading water gently across the surface to keep it moving without blasting plants or fish directly, which matters for both gas exchange at the surface and for not disturbing a delicate carpet or stem planting nearby. The inflow side often uses a similarly shaped glass piece with a guard to keep shrimp and small fish from being pulled into the filter.

Because lily pipes are glass, they need to be handled and cleaned carefully to avoid chips or cracks, and the connecting tubing has to be sized correctly to fit snugly without leaking. A common mistake is choosing a lily pipe diameter that restricts flow compared to the canister's rated output, which quietly reduces filtration and surface movement even though the tank looks tidier.