
Nemo Long-Tail Male Betta (Betta splendens)
24–30°C · pH 6–7.5 · 20L
An Alien Green male ornamental Betta for a calm, heated, planted aquarium. Keep this territorial male singly; individual colour, pattern and finnage vary.
Adult size is the maximum length this species reaches at full maturity (scientific sources). The livestock you receive will be younger and smaller — pick a size above for the actual shipping size. Product-photo provenance and any image-specific limitations are stated on the listing.
Betta sp. (Alien Green ornamental trade form)
An Alien Green male ornamental Betta for a calm, heated, planted aquarium. Keep this territorial male singly; individual colour, pattern and finnage vary.
Adult size is the maximum length this species reaches at full maturity (scientific sources). The livestock you receive will be younger and smaller — pick a size above for the actual shipping size. Product-photo provenance and any image-specific limitations are stated on the listing.

For one typical domestic Betta splendens, start with at least 20 litres, a mature filter, thermostatic heater, separate thermometer, gentle flow, a secure lid with surface access, and plants or refuges. Keep one male per aquarium.
Maintain these water conditions for optimal health and vibrant colors
The Alien Green male Betta is an ornamental trade form, valued for its metallic green appearance. Individual colour, pattern and finnage vary. This is a live fish with real character: intelligent, responsive and best kept as a single male in a thoughtfully arranged aquarium. The “Alien” line is known for its iridescent, almost armour-like appearance, making it a standout choice for aquarists who want something truly eye-catching.
Although hardy compared with many tropical species, male Bettas are not community fish in the traditional sense. They do best in a calm, warm aquarium with gentle filtration, plenty of cover and regular maintenance. When kept correctly, they can thrive and often become surprisingly interactive with their keeper. The listed grades are L and 3–4 cm. Use the size selector to check availability and the price for your chosen grade; L is a supplier grade, not an exact centimetre measurement.
Please ensure your aquarium is fully cycled and prepared before ordering. Our Betta care guide explains how to plan a heated, filtered setup.
| Care Factor | Recommendation |
|---|---|
| Trade Form | Alien Green male Betta; ornamental form |
| Common Name | Alien Green male Betta |
| Care Level | Moderate |
| Temperament | Semi-aggressive |
| Adult Size | 6-7 cm body, longer with fins |
| Minimum Tank Size | 40 litres for a single male |
| Temperature | 24-28°C |
| pH | 6.5-7.5 |
| Diet | Carnivorous; high-protein pellets, frozen and live foods |
| Lifespan | 3-5 years |
| Tank Region | Top to middle |
Wild Betta splendens originates from the warm, slow-moving waters of Thailand and neighbouring parts of South-East Asia. In the wild, Bettas inhabit rice paddies, floodplains, ditches and shallow marshes where the water can be warm, still and low in oxygen. Their labyrinth organ allows them to breathe atmospheric air, which is one reason they can cope with conditions that would challenge many other fish.
Alien is an ornamental trade name, rather than a guarantee of a pure wild species or particular parentage. The International Betta Congress standards include Alien in their hybrid show classes. Keep this male as an ornamental Betta in warm water, with gentle flow and clear access to the surface.
A single male Alien Green Betta should be housed in a secure, heated aquarium with a lid. Bettas are excellent jumpers and appreciate calm water with minimal surface disturbance. A tank of 40 litres or more gives enough room for swimming while still allowing the fish to feel secure. Dense planting, broad-leaved plants, driftwood and caves help break up sight lines and reduce stress.
Use a gentle filter such as a sponge filter or a low-flow internal filter. Strong currents can tire Bettas and damage their fins. Smooth décor is important because long-finned males can snag on sharp ornaments or rough plastic plants. Floating plants are especially beneficial, as they provide shade and resting points near the surface.
Recommended water parameters are 24-28°C, pH 6.5-7.5, with stable, clean water and low ammonia and nitrite. Bettas prefer consistency over frequent swings in temperature or chemistry. Regular partial water changes are essential, particularly in smaller aquariums, to maintain excellent water quality and protect fin health.
Alien Green Bettas are carnivores and need a varied, protein-rich diet. A quality Betta pellet can form the staple, but it should be supplemented with frozen or live foods such as daphnia, brine shrimp, mosquito larvae and bloodworm. Variety supports colour, condition and natural behaviour.
Feed small portions once or twice daily, offering only what the fish can consume in a couple of minutes. Overfeeding is a common issue with Bettas and can lead to bloating and poor water quality. A fasting day once a week can be helpful for some individuals, provided the fish is otherwise healthy and feeding well.
Male Bettas are best kept singly. Their territorial instincts mean they are not suitable for housing with other male Bettas or similarly shaped, brightly coloured fish. In some larger, carefully planned aquariums, they may be kept with peaceful species that do not nip fins, but compatibility depends heavily on the individual fish’s temperament.
Choose tank mates that are calm, non-nippy and not overly active. Avoid species that may provoke aggression or damage fins. Always monitor introductions closely and be prepared to separate fish if needed. A heavily planted tank with visual barriers can improve success, but keeping this male on his own is often the safest option. Read our Betta tank-mate guide before considering a community setup.
Use the care information to decide whether an Alien Green male Betta suits your aquarium. Check the selected grade and current price before ordering, and prepare suitable housing so this territorial male has a calm space of his own.
Whether you are adding a statement fish to a planted display or selecting a standout male for a dedicated Betta setup, the Alien Green Betta is a superb choice. With the right environment, this striking fish will reward you with colour, personality and years of enjoyment.
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TRACEY DURRANT · 7 Oct 2026
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