Black kuhli loaches are among a handful of commonly kept freshwater aquarium fish species. They need pristine water conditions, which makes them slightly challenging for beginner aquarists to keep, but they adapt readily to a fairly wide variety of tank conditions. Their playful group antics make them worth the effort.
In the wild, black kuhli loaches, like most loach varieties, inhabit rivers and streams that have good oxygenation. In captivity, they thrive in tanks with moving water, which you can accommodate by adding a filter with a powerhead, or even a simple bubble strip. They require clean, well-filtered, slightly acidic water -- a pH of around 6.0 to 7.0 -- and an average temperature between 75 and 85 degrees Fahrenheit. Small groups of black kuhli loaches require a tank with capacity no less than 20 gallons. Tank substrates should be smooth and free of sharp edges, which could otherwise injure the fish while they scavenge for food.
Kuhli loaches are peaceful, gregarious fish who do well in community aquariums with other nonaggressive species. Their wormlike appearance can make them seem like tasty treats to larger fish, so take care to either keep smaller fish with your kuhli loaches or provide plenty of hiding spaces for the loaches to retreat to if harassed. Black kuhli loaches are social; keep them in groups no fewer than three. They will be much bolder and more playful if kept in small schools of six or more fish.
Kuhli loaches spend almost all of their time at the bottom of the tank, coming out to scavenge in the mornings and evenings. They are excellent aquarium cleanup crews, removing leftover bits of food that drift down to the substrate. They will eat flake food, sinking pellets and live foods such as bloodworms and tubifex worms. As with most aquarium fish, they'll stay in the best condition if you provide a varied diet of prepared and live foods in proper moderation. Remove remaining food as soon as the fish stop feeding so it doesn't foul the water.
Kuhli loaches are notoriously shy in captivity; they will wriggle into just about any opening they can fit into in order to escape or hide. Cover intake and outtake tubes on filters with filter foam or something similar, or place them out of reach of the fish to prevent them from getting stuck or even killed. Provide plenty of hiding places in the aquarium to make them less inclined to scout out “caves” in dangerous locations.