- Scientific name: Crinum thaianum
- Synonym: -
- Common name: Onion plant
- Family: Amaryllidaceae
- Group: Aquarium plants
- Max height: 80 cm (sometimes 1,5 m)
- Distribution: Asia; Thailand
- Habitat: In flowing waters rooted deep in the substrate in a water level of up to 2 m.
- Substrate: Nutrient rich
- Placement in aquarium: Background
- Planting density: 3-5 plants for 20 cm2
- Lighting needs: Moderate to bright
- Temperature: 22-30°C
- pH: 6,5-7,5
- Hardness: 3-12 NK°
Description: This large plant will produce leaves up to 60 in (150 cm) long, so although established plants can be cut back occasionally without any harm, use it carefully. The ribbonlike leaves are 0,8 in (2 cm) wide. Once they reach the surface, they will float horizontally on the water. The onion plant adapts well to the aquarium environment and is an undemanding species.
Crinum thaianum is a specifically adaptable and quick-growing species with only moderate light requirements. It will prosper in both soft and hard water at temperatures from 22 to 27 °C and requires a nutrient-rich substrate at least 8 cm deep in which the strong root system can spread out. Side and rear panels, especially in high aquariums, can very effectively be decorated with Crinum thaianum by densely arranging several specimens next to each other. Due to quick growth, a dense thicket of long floating leaves will develop on the water surface after a short time. Propagation through bulbils in older plants is achieved more often than in Crinum natans.