The Black Kuhli Loach, Pangio oblonga, is a close relative of the Kuhi loach, Pangio kuhlii, but is not as popular in aquariums because of its plainer colouring. The Black Kuhli loach comes from India, Bangladesh, Myanmar, Cambodia, Laos, Vietnam, Thailand, Indonesia and Malaysia.
The maximum length of this fish is about 8 centimetres (3 inches), but because it is a thin eel like shape, this is still a small fish.
This is a tropical fish and a temperature of between 23 and 28 degrees C (between 73 and 82 degrees F) is acceptable. This fish comes from soft acid water and the usually recommended conditions for them in an aquarium are a pH of between 6.2 and 7.2, with soft water. Although it seems logical to approach the water parameters of its natural habitat, Richard Bias of New Jersey, USA has kept and bred this fish with a pH of 8.0 and relatively hard water with a gH of 18-22 and a kH of about 20.
It may be that keeping the water clean and with consistent pH and hardness is more important than the actual values of the parameters.
In the wild their habitats often have a sandy bottom. This is generally recommended for aquariums, but Mr. Bias used small rocks of up to 2.5 cm (1 inch in diameter). I have also had success with keeping this species using a substrate of small pebbles.
In the wild they are used to plants and an aquarium should have plenty of live plants.
Black Kuhli Loaches are omnivores, but their diet requires a reasonable amount of animal based food. My Kuhlis seem to particularly like frozen blood worms (so do many fish). I also give them frozen brine shrimp once a week. They will also eat normal fish foods like flakes.
They are bottom feeders and only eat what falls to the bottom.
Black Kuhlis are partially nocturnal. Combined with this they will burrow into the substrate and are good at hiding in the plants, so you may not see them much. They are difficult to catch.
Although they cannot be described as a schooling fish, they seem to do better in groups; the larger the better.
They are peaceful fish and can be kept with other small peaceful fish. They are a good inhabitant for a well planted community tank of at least 50 litres (13 US gallons).
When in breeding condition the females become distinctly fatter than the males.
Breeding in the Wild
It is believed that in the wild this fish breeds in flooded forests. The forest floor may well have much organic debris from the trees and the baby loaches probably grow amongst these; feeding on the rich animal and vegetable food which grows in this environment.
Breeding in an Aquarium
I suggest that two likely requirements for success are excellent feeding including rich foods like blood worms, and a substrate that will allow the babies to live and feed in.
Although the known single example of successful breeding in aquariums is not enough to make firm conclusions, it suggests that breeding in a community tank is not impossible.
In the wild this fish is not threatened and seems to be able to reproduce itself very well. I suggest that the rarity of breeding success in aquariums could be due to the likelihood of the conditions in the wild that stimulate breeding being quite different from those that the adults normally live in.