Aponogeton rigidifolius

Aponogeton rigidifolius is endemic to the fast-flowing rivers and streams of Sri Lanka, where it is adapted to clear, well-oxygenated, slightly acidic water. It is one of the most distinct and desirable Aponogeton species for aquarium use, producing long, strap-like leaves in deep olive-green to brownish-green with a strongly corrugated, hammered surface texture and leathery, firm consistency — quite unlike the soft, translucent leaves of most other Aponogeton species.

A key advantage of A. rigidifolius over many other Aponogeton species is that it does not require a dormancy period — it grows continuously year-round and can remain productive as an aquarium plant for many years. The corm grows slowly larger with time, and established plants of several years' growth are truly impressive specimens. It is more tolerant of slightly cooler conditions than most tropical Aponogetons.

This species is best suited to soft, slightly acidic to neutral water and grows more reliably in such conditions. In hard, alkaline water it can persist but growth slows and new leaves may be smaller and less well-formed.