The Pygmy Rainbowfish was described by Allen in 1974 and its scientific name is Melanotaenia pygmaea. Collecting Pygmy Rainbowfish is a bit cumbersome since this species inhabits such a remote part of the Australian wilderness, but it is easy to breed in captivity.

Description
Just like the name suggests, the Pygmy Rainbowfish is a small rainbow that stays below 5 cm (2 inches) in length. The male is more colourful than the female and boasts a glistening blue back and pale yellow fins. The body is decorated with a prominent mid-lateral stripe.

Geographical distribution, habitat and conservation
The Pygmy Rainbowfish lives in streams the West Kimberly district, which is located in the northern part of Western Australia. As far as we know, it can only be found in two minor tributaries of the Prince Regent River. The Pygmy Rainbowfish inhabits rivulets and pools that form under small waterfalls, and it is therefore used to a high oxygen content. Powerful aeration is important if you want to keep this fish in your aquarium.    

The Pygmy Rainbowfish is listed as “Lower Risk: near threatened” in the IUCN Red List of Threatened Species.

Keeping Pygmy Rainbowfish in aquariums
The Pygmy Rainbowfish is not tricky to keep as long as you avoid using chlorinated water in the aquarium. If you know that the tap water in your area contains chlorine, use a de-chlorinator or a de-chlorinating method before you use it for water changes.

Try to mimic the natural environment of the Pygmy Rainbowfish when you arrange the aquarium and include plenty of hiding spots. Rocks, driftwood and live plants are highly appreciated. In the wild, Pygmy Rainbowfish is often found over solid rock bottoms and sandstone terraces where aquatic plants are scarce.

The Pygmy Rainbowfish is small and peaceful and can be kept with other non-aggressive species of similar size. It is frequently combined with other small species of Rainbowfish in mixed rainbow aquariums. During the breeding period, the male fish may harass the females and it is therefore important to provide the females with an abundance of good hiding spots. Always keep several females for each male.

Changing 25% of the water every second week is often enough, but this figure might need to be adjusted to fit your particular aquarium. A small and crowded aquarium needs more frequent water changes than a large aquarium with few fishes. Keep the water temperature in the 23-28 degrees C (73-82 degrees F) range. The pH-value should be around neutral, from 6.8 to 7.2.  

Breeding Pygmy Rainbowfish

Both sexes can become sexually mature when they are just slightly longer than 2 cm (0.8 inches). The Pygmy Rainbowfish can be bred in groups or in a harem consisting of one male and 2-3 females. As mentioned above, a group of Pygmy Rainbowfish should always contain several females for each male. Provide the fish with a suitable spawning medium, e.g. java moss or a spawning mop.

The spawning will normally take place in the morning. Check the aquarium for eggs each morning, since the adult fish can devour the eggs quite rapidly. The thicker the spawning medium the better, since it makes it harder for adult fish to find the eggs. Move the spawning medium to a separate container when you notice eggs. The container must have sufficient aeration. If you keep the water temperature around 25 degrees C (77 degrees F) you can expect the eggs to hatch within two weeks. Feed the fry infusoria and liquid fry food until they are large enough to devour newly hatched brine shrimp.

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Other Australian Rainbowfishes

Cairns Rainbowfish
Threadfin Rainbowfish
Lake Eacham Rainbowfish
Exquisite Rainbowfish
Murray River Rainbowfish
Slender Rainbowfish
MacCulloch’s  Rainbowfish
Black-banded Rainbowfish
Western Rainbowfish
Chequered Rainbowfish
Eastern Rainbowfish
Desert Rainbowfish
Banded Rainbowfish
Ornate Rainbowfish