Stefan van der Voort explains how to keep the very difficult, very expensive and very rarely sold Betta macrostoma.

Common name: Peacock betta, Brunei beauty.

Scientific name: Betta macrostoma, Regan, 1910.

Origin: Parts of Borneo.

Size: A chunky 9-11 cm/3.5-4.3.

Water: In the wild, slightly acidic (pH ranging from 6.5-7.5), 10GH. Water temperature should be cooler than normal at 20-25C/68-77F.

Aquarium: A large aquarium is strongly advised, and it must be a species tank " Betta macrostoma cannot be kept with other fishes. This is one of the most sensitive Betta species, and it is highly advisable to replicate wild conditions for success. Two pairs can be kept in larger tanks (over 1 m/39).

The tank should be furnished with plants and wood and should have a gravel bottom. Carry out 20-25% weekly or twice-weekly water changes.

Diet: Easy to feed. Accepts most frozen and live foods, but not dried foods. Try brineshrimp, Daphnia, glassworms, krill, Mysis and (in appropriate amounts) bloodworms.

Adult colouration: Considered by many to be the most beautiful of its genus. Males have two black horizontal bars running along the side with an orange cheek that also contains a large black blotch. The dorsal fin has an impressive eye-spot that has a black colour and is surrounded by orange patches. Its caudal fin has curved bars with orange patches while the rest of its fins remain dusky.

In its most beautiful colouration, the body is a magnificent orange. Females are a simple brown and may show the same horizontal bars on the flanks, or maybe a faint orange at best.

Breeding: A paternal mouthbrooder, best kept one pair per tank. If fed and kept well, the female will soon become gravid and may spawn shortly after. The male wraps himself around the female and gametes are released during the embrace. Then something happens that so far only B. macrostoma is known to do; instead of shooting the eggs back to her partner, they ~kiss to pass on the eggs. The male broods the eggs for 30-35 days.

The fry are large at 5-10 mm, and may be cared for by both parents for three to seven days. They need to be fed twice a day on brineshrimp nauplii and microworms. After a month they start to resemble their parents and show horizontal bars. From there on, they should be easier and you can switch to larger foods.

Notes: In Brunei, this is a protected species and collecting it without approval from the Sultan of Brunei leads to serious sentences. This Betta is said to be the Sultan s favourite.

B. macrostoma is easily stressed and can crash into the glass when frightened, sometimes resulting in death. Keep stress to a minimum!

Availability: Very rarely seen in shops on account of its difficulty. It is more common in hobbyist circles, where fishkeepers are more skilled in keeping the fish alive and healthy. These specimens were spotted at Maidenhead Aquatics @ Oxford (01865 876516) in the summer of 2006.

Price: Typically an extremely expensive species. Expect to pay around 105, or two for 200 " if you are lucky enough to find it.