Water onion (Crinum thaianum) care guide

Group

Plants

Other names

Water onion, Thai onion plant, Onion plant

Family

Amaryllidaceae (amaryllis family)

Origin

Coastal plain of Ranong and Phang Nga provinces, southern Thailand

Water

freshwater

Maximum size

200 cm

Temperature

22–30°C

pH

6–8

Care level

beginner

Lighting

Low light; CO2 not needed but helps

Flow

Tolerates moderate to strong flow

Care

The water onion is a bulb plant from a small area of southern Thailand, where it grows on the banks of fairly fast streams with its bulb in the sediment and its leaves streaming in the current. The ribbon-like, bright green leaves are about 2.5 cm wide and commonly 60–200 cm long. Old plants can send a stem to the surface with fragrant white lily-like flowers. It needs plenty of space: plant it at the back or in a corner of a large, tall tank, with about the top two-thirds of the bulb above the substrate, as a buried bulb tends to rot. It also grows in warm outdoor ponds. Tropica rates it easy, with low light and CO2 needs and medium growth. Wikipedia gives 22–30 °C and recommends a rich substrate; it copes with changes in temperature and light. pH figures are our estimate, not from the sources. Conservation: it is endangered in the wild, with only a small, fragmented and shrinking population, threatened by bulb collecting and river dredging. Buy nursery-grown plants. Sources: Tropica (tropica.com/en/plants); Wikipedia (en.wikipedia.org/wiki/Crinumthaianum); Wikipedia, List of freshwater aquarium plant species. Checked October 2026.

Breeding

By daughter bulbs that form beside the mother bulb; separate and plant them once they have their own roots.

Compatibility and tank mates

Tough leaves that herbivorous fish leave alone, so it suits cichlid and other "difficult" tanks. Good with most tropical fish.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.