Eelgrass

The species name 'spiralis' does not refer to the leaves but to the female flower stalk, which coils into a tight spiral after pollination to draw the developing fruit underwater. This distinguishing feature separates true Vallisneria spiralis from the many straight-leaved vallisneria forms sold under the same name in aquarium shops.

This classic background plant has long, narrow bright green leaves that sway in the current. It spreads aggressively by runners once settled, filling the background of a large tank in a few months. In smaller tanks the runners need to be trimmed back or contained within a buried plastic pot to prevent the plant from taking over the whole substrate.

Moderate light and neutral to slightly alkaline water suit it best. CO₂ is not required, which makes it one of the most reliable plants for low-tech setups. Like all vallisnerias, it is sensitive to liquid iron fertilisers near the crown — root tabs pushed into the substrate near the runners are the safer option. The plant is widely distributed across Europe, Africa, and Asia and tolerates a broad range of conditions once established.