Betta Trading

Kuhli Loach

The Kuhli Loach, Pangio kuhlii, is a small eel like fish.  It comes from Indonesia, Malaysia and Thailand.  Other names include Coolie Loach, which is a clear miss-spelling of Kuhli; both these words are pronounced in the same way.  It is also called “Prickle Eye” because it has a prickle near its eye. This prickle probably gives this fish some protection from predators.

Length and Longevity

The Kuhli Loach will supposedly grow up to 12 centimetres (4 and a half inches) long, but I have never seen one this big.  Most of the ones available are much smaller than this.  One of the reasons for this variation is that there are several subspecies of Pangio kuhlii, and the size they grow to varies a lot. 

They have been reported as living up to 10 years.


Water Conditions

The Kuhli Loach is an equatorial fish; the main areas it is from are a little to the south of the Equator.  It needs warm water, and a temperature of between 24 and 30 degrees C (between 75 and 86 degrees F) is suitable.  They can survive a slightly higher or lower temperature than this range, but I do not recommend it.

In the wild this fish is mainly found in slowly flowing streams with a sandy bottom with a layer of organic matter from the surrounding forests in many places on the stream bed.  The water in these streams tends to have a fairly low mineral content and to be soft and acidic.  There are plants growing in sections of these streams.

In an aquarium, they will adapt to a moderate hardness and can take a hardness of up to 10 dH, and possibly a little higher.  A pH of up to 7.5 is generally tolerated.  The water needs to be reasonably clean in the sense of not having a large build-up of fish wastes.


You should avoid any sharp substrates and fine river sand is the normal choice.  I have also had success with using large (6mm or more) rounded pebbles.

These fish not only search the surface of the sand for food, they will go right into it.  I have seen them dive straight into the sand to avoid being caught.  With larger pebbles they will go between the pebbles looking for food.


These fish seem to like densely planted aquariums.  Including some floating plants is also a good idea.


Kuhli loaches are omnivores with a requirement for some animal based food.  They will eat flakes and pellets.  One of their favourite foods is frozen bloodworms.  They also like frozen brine shrimp.

This is a bottom feeding fish, so it is necessary for some of the food to reach the bottom.

The Kuhli Loach has the distinction of being the most difficult fish to catch in a planted aquarium.  It is closely followed in this by the Black Kuhli Loach.


Although the Kuhli Loach is not a schooling fish in the normal sense, they seem to need company.  A single Kuhli may be able to live all right in a tank, but will tend to be hidden nearly all the time during the day.  A group of perhaps eight of these interesting fish will behave quite differently and are much more likely to come out and show themselves during the day.

This is a small peaceful fish, and is a suitable inhabitant for a community aquarium of small peaceful fish.


Most of the time there is not a big difference in appearance between the sexes, but the male is more muscular in the front part of his body.  The male also have larger pectoral fins with more black on them than the females.

When they are ready to breed the gender becomes more obvious with the female’s lower body becoming distinctly fatter with greenish coloured eggs visible.

These fish probably reach sexual maturity at about 2 years old.

Breeding in the Wild

Wild Kuhli Loaches usually breed in December and January.  In the areas they come from, the wettest three months are December, January and February, so they breed in the early part of the wet season when the water level is rising.  They apparently breed in very shallow water, in areas which are dry part of the year.  Some of the breeding areas would not even be part of the stream bed, but would be normally a forest area.  These flooded forests have a large amount of food both for the adults and for their babies.  The breeding appears to be communal with a group of Kuhlis taking part rather than just one pair.

This fish is not threatened in the wild so they must be breeding successfully.

Breeding in Aquariums

There are many reports of this fish breeding in aquariums, but nearly all of these are of accidents rather than planned breeding.  Most of these reports involve community aquariums.

I have yet to see a well-documented account of this fish breeding when this was planned, but there are a number of bits of information which can be pieced together.

Weather Predicting

This fish will react when it is about to rain.  It’s in the same family as the famous weather loach whose rain predicting abilities appears to rival the most advanced meteorological techniques.  Both the weather Loach and the Kuhli loach will swim wildly as if they are ready to spawn when rain is coming.  It is generally believed that they are reacting to a change in air pressure.  We should remember that our Kuhli Loaches are kept inside in an aquarium heated to a constant temperature, and that the pressure they are subjected to includes the pressure caused by the depth of the water in the aquarium.  This depth may vary from time to time. 

I wonder if we are underestimating these fish.  The change in air pressure is not the only thing that happens before rain.  The rain in the areas they come from will be largely accompanied by electrical storms and the atmosphere before thunder storms has a different proportion of negative to positive ions from normal.  Humans can feel the effects of this.  Possibly this is also used by fish in predicting weather.


To breed it is obvious that the fish will need to be well fed so they have enough nutrition to grow the eggs and sperm.  Meaty foods like bloodworms, brine shrimp, daphnia etc will be helpful in this.

Stimulating Spawning

It appears that conditions simulating those at the start of the rainy season in their native habitat are likely to encourage spawning.  These conditions will include an increase in water level by the addition of pure water.    This will reduce the hardness of the water.  A reduction in the water temperature of 5 degrees C (9 degrees F) may also help.


This fish seems more likely to breed if there are a good-sized group of them.  The female can lay up to 400 eggs.  They are strongly adhesive, and stick to plants, including floating ones.

The eggs hatch in about 24 hours.  The babies are about 7 millimetres long after hatching.  In many cases the fry have succeeded in growing on the food present in a community tank.

Common Names

Common names for this fish in English include ‘Kuhli Loach”, “Coolie Loach”, “Giant coolie loach”, “Leopard loach”, “Slimy loach”, and “Slimy myersi”.

In French, it ii called “Kuhli” or “Loche coolie”, or “Loche léopard" or “Loche svelte” or “Serpent d'eau”.

Scientific Name

The accepted name is “Pangio kuhlii” (Valenciennes, 1846). 

Sources and Picture credits

Fishbase. Kuhli Loaches spawning, Baby Kuhli Loaches.

  The second picure above the water conditions section is from Brentwod Aquatics

The picture of the large number of Khuli Loaches below the section about companions is copyright AGUAlity Tropical Fish Wholesale, and is used with their kind permission.

Steve Challis