Crinum thaianum

Scientific name: Crinum thaianum

Family: Amaryllidaceae

Usual maximum size in aquariums: 60 - 200 cm (23.62 - 78.74 inch)

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Recommended pH range for the species: 6.8 - 7.5

Recommended water hardness (dGH): 4 - 18°N (71.43 - 321.43ppm)

0°C 32°F30°C 86°F

Recommended temperature: 24 - 28 °C (75.2 - 82.4°F)

Reproduction of the plant: Bulb shoots

Origin (in the wild): South Asia

How fast these plants grow: Normal

Recommended substrate: Gravel

Demands on lighting: Medium

Ideal placement in a fish tank: Background

Common Names

Onion Plant, Water Onion Plant

Origin

Crinum thaianum is native to southern Thailand, where it grows along the banks and shallow waters of rivers and streams. In nature, it is often found partially submerged, but it thrives fully submerged in aquariums.

Propagation

This plant reproduces vegetatively by producing daughter bulbs. When well-established and healthy, the main bulb will develop smaller bulbs at its base. These can be carefully separated once they are at least one-third the size of the mother bulb. When planting, make sure that the top of the bulb remains visible above the substrate to prevent rotting. New plants can then be planted in other areas of the tank.

Difficulty

Easy

Short Description

Crinum thaianum is a true aquatic plant and an excellent choice for large aquariums. It produces long, ribbon-like leaves that are both decorative and resilient—fish rarely nibble on them, making it ideal for tanks with herbivorous species. It requires a clean, nutrient-rich substrate and water column to thrive. Leaves can grow exceptionally long and may need occasional trimming at the water surface. This will not harm the plant. Due to its size, it is best used as a background or specimen plant in large aquascapes.

FAQs

• Should I bury the whole Crinum thaianum bulb?

  No, the top third of the bulb should always remain above the substrate. Fully burying the bulb can lead to rot and plant death.

• How fast does Crinum thaianum grow?

  Growth is moderate. Once established, the plant will produce long, flowing leaves, and over time, daughter bulbs will appear. CO₂ and good nutrients can enhance growth.

• Is Crinum thaianum suitable for tanks with plant-eating fish?

  Yes, the tough, fibrous leaves of this plant are usually ignored by herbivorous fish, making it a good choice for such setups.

• Can Crinum thaianum be grown emersed?

  While it can survive in shallow, marsh-like conditions, it is best kept fully submerged in aquariums, where it thrives and develops its characteristic long leaves.

• What are signs that Crinum thaianum needs more nutrients?

  Yellowing or transparent leaves, slow growth, or a weak root system may indicate a lack of nutrients. Supplement with root tabs or a rich substrate.

• Tips for long-term care

  To keep Crinum thaianum healthy over the long term, ensure stable water parameters, regular substrate cleaning, and occasional root fertilization. Avoid disturbing the bulb once it has rooted, and prune older or damaged leaves close to the base to encourage fresh growth.