Coolie Loach Fish Species Profile

The coolie loach is a bottom-dwelling fish that enjoys burrowing in the sand and exploring all of the hiding places in your tank. Even with its eel-like shape and fascinating burrowing habits, these fish are still surprisingly social and prefer the company of others of their own kind. The coolie loach is most active at twilight and at nighttime, both in nature and in the home aquarium, while remaining hidden during the day. There are many subspecies of this fish, however, all coolies have the same dietary and habitat needs, so knowing the specific subspecies is not critical.

Characteristics

Origin and Distribution

Originating from Southeast Asia, the coolie loach is indigenous to the streams of Borneo, Java, western Malaysia, Singapore, Sumatra, and Thailand. Originally named Cobitis kuhlii, and later changed to Acanthophthalmus kuhlii, the current scientific name of this fish is Pangio kuhlii. Many references still utilize former scientific names.

Pangio kuhlii is one of two dozen species of kuhlis, a number of which closely resemble each other. The subspecies Pangio kuhlii sumatranus and Pangio kuhlii myersi have been described based on differences in coloration and markings. P. sumatuanus (also known as the Sumatra Kuhli) has fewer and darker bands than Pangio kuhlii. Sporting even wider bands is the Pangio kuhlii myersi. Although Pangio kuhlii remains the most popular and readily available of the coolie loaches, it is not unusual to purchase an incorrectly named loach.

Colors and Markings

Coolie loaches have an eel-like body that is yellow to pink in color, with multiple dark brown bands or stripes that partially or fully encircle the body. The body and stripe color patterns vary based on subspecies. The coolie loach possesses no lateral line, the fins are small, and the dorsal fin is located on the lower third of the body, much closer to the tail than the head.

The eye of the coolie is covered by a thin layer of transparent skin and is hidden under one of the dark bands. Below the eyes are a pair of sharp spines that rise if the fish is threatened, making it difficult for a predator to swallow them or for an owner to net them; take special care when doing so. The mouth of the coolie loach points downward and is surrounded by four pairs of barbels.

Tankmates

Coolie loaches are happiest when kept in groups of a half-dozen or more other coolies, and they are easily kept with non-aggressive fish. When kept singly they are quite shy and will remain hidden most of the time. Avoid keeping coolies with large or territorial fish, such as cichlids; instead choose small fish such as danios, rasboras, and tetras.

Coolie Loach Habitat and Care

In nature, the coolie loach lives in locations where there is clear, slow-moving water running over sand. They will tolerate a range of water parameters but prefer water on the acidic side with slightly colder temperatures in the mid-70s Fahrenheit. The smooth substrate is a must as these obligate burrowers will be injured by substrates having rough edges. Sand is the preferred substrate for these fish.

Make sure the tank is tightly covered as coolie loaches will jump out of the tank, particularly when startled. The inlet tube on the filter needs to also be covered with mesh or a sponge, as there are many documented cases of loaches swimming up the inlet tube and getting trapped in the filter. Owners have reported cases in which coolie loaches have disappeared for months, only to be found under the UGF or inside a canister filter, still very much alive. Take a headcount on your coolies to ensure you haven’t lost one or the lost fish may suffer and starve.

Coolie tanks should have plenty of safe hiding places, preferably in low, live plants when possible. Rocks, driftwood, and caves are all the best decor for coolie loaches. Keep lighting subdued, however, a well-lit tank is suitable as long as it is heavily planted, thus offering shady places for the loaches to hide. Place a moonlight in the tank so you can observe their nocturnal activities.

Coolie Loach Diet and Feeding

Live foods are the preferred diet for coolie loaches. However, they will accept a variety of foods, including frozen, freeze-dried, tablets, wafers and flake foods. The key is to remember that they need smaller foods that will sink. Always feed coolies at night.

When it comes to live foods, bloodworms are readily accepted as well as glass worms, tubifex, and daphnia. Frozen versions of these foods are the next best option. Feed live or frozen foods a couple of times per week to augment dry foods.

Gender Differences

There are no readily discernible differences between coolie loaches when they are not breeding. Some hobbyists have observed that males have larger pectoral fins, with thickening of the second ray. Once females are carrying eggs they become noticeably larger, sometimes in the extreme. In some cases, it's even possible to see the green-colored eggs through the skin of the female's abdomen.

Breeding the Coolie Loach

Breeding of coolie loaches is challenging, but it has happened in captivity. The breeding tank should have low water levels, very dim lighting, and floating plants, which will be used by the female when laying her eggs. Water pH should be about 6.5, and the water hardness should be lowered. Dense vegetation will help promote spawning. The more comfortable the coolies become with their environment, the greater the chance of spawning.

Because coolies are communal spawners, keeping a larger group will increase the likelihood of spawning. Fish do not reach sexual maturity for two years, which means you may have to be patient if your fish are young when you purchase them. Condition the fish with plenty of live food to encourage spawning.

As females near the time to lay their eggs, they will grow very large. When ready to spawn, the female will release bright green adhesive eggs, usually on the underside of the floating plants. To ensure the greatest number of fry survive, remove the adult fish to their original tank once the eggs have been laid.

Eggs will hatch in approximately 24 hours, and they can number up to several hundred. Infusoria, generally present in mature live plants, is an ideal first food. Freshly hatched brine shrimp are also a good first food. Commercially prepared fry food or finely crushed flakes are suitable as food for coolie loach fry.

More Pet Fish Species and Further Research

If coolie loaches appeal to you, and you are interested in some compatible fish for your aquarium, check out:

• Weather Loach Species Profile
• Long Horseface Loach Species Profile
• Yoyo Loach Species Profile

Check out additional fish breed profiles for more information on other freshwater fish.