All You Need to Know About Keeping Coolie Loaches

by brettb

How to keep Coolie Loaches in your tropical fish tank. Learn how to care for these very cute tropical fish.

A tropical fish that looks like a snake? Why don't you have any of these cute guys in your tropical fish tank?


Coolie Loaches are the coolest tropical fishes around! If you have a tropical fishtank then you owe it to yourself to buy some of these delightful little fish.

Strangely, considering so many people keep tropical fish, not much is known about them! Coolie Loaches are a particularly mysterious fish. Here's what I know about Coolies, and some notes and observations from keeping them for seven years now.

Coolie Loaches have the latin name of Pangio Kuhlii. They're also commonly known as Kuhli Loaches.

There are a few photos of Coolies on this page. As you can see they're long rather wormlike fish. In fact some people might think you have some snakes in your fish tank!

They grow to about 10cm long. Sometimes they can grow very fat.

Two species exist. The common Coolie is dark brown with orangy-yellow stripes. The stripes are unique to each fish and allow you to tell them apart.

There's also a Black Coolie Loach. This fish is somewhat rarer and your local fish store might not have any of these in stock.

My black Coolies are smaller than my stripy Coolies - I don't know if they're always like this.

Photos of Coolie Loaches

Black and Stripy Coolie Loach
Black and Stripy Coolie Loach
Coolie Loach Peeking Out from His (or Her) Castle
Coolie Loach Peeking Out from His (or...

Looking After Your Coolie Loaches

Coolie Loaches are practically indestructable! As such they're great beginners fish.

My Coolies once got whitespot, but they were easily treatable with the standard fish medicine for this common disease.

Coolies live at the bottom of the tank, and they love somewhere to hide away. They tend to be more nocturnal, so a rock or a castle to sleep in will please them no end.

Coolie Loaches are very sensitive to noise and vibrations, so keep your tropical fish tank in a quieter part of your home or office. Of course it's best not to allow anyone to knock on the glass!

You'll find that if Coolies panic they swim around the tank very quickly indeed. They often also turn off their coloration and go very pale. They also do this in the night, so don't be alarmed if your fish changes color!

Sometimes Coolie Loaches go mad and swim around the tank for hours on end. This seems to happen more in newer tanks where the water is clean and there isn't much to eat. Nowadays my Coolies tend to hide away in their castle, appearing only at feeding time or when I'm cleaning the tank. The black Coolies seem to like swimming around more.

Nobody really knows why they do this strange swimming activity. Maybe it's related to filter feeding, or maybe it's a mating ritual. Maybe they just like having fun! Let me know if your own Coolies do it (the comments section is below).

One cool thing about Coolies is that if you fill your tank with sand rather than gravel then the loaches will sift the sand through their gills looking for tasty morsels to eat. This looks really cool!
One thing to be careful of is that like other loaches, Coolies have barbels on their heads near their eyes. These can get caught in nets if you're catching them, so be very careful!

Speaking of nets - Coolie Loaches are famously difficult to catch! So bear that in mind if you need to move house a lot.

Feeding Your Coolie Loaches

Coolie Loaches eat anything!

In fact, I don't actually feed my Coolie Loaches anything, they just eat all the left over food that falls to the bottom of the tank.

I've also heard that if there isn't any food in the tank then they'll just eat bacteria or other stuff that's too small to see.

So don't worry about your Coolies going hungry! If your fish tank isn't brand new then there will be enough microscopic bacteria, algae or fungi for them to live on.

More Coolie Loach Photos

Coolie and Sucking Loach
Coolie and Sucking Loach
One of my really long Coolies
One of my really long Coolies

Tankmates for Coolie Loaches

Coolie Loaches tend to do better in smaller fish tanks, i.e. those up to 150 gallons capacity. They'll also prefer to be with more placid fish like Neon Tetras, Guppies, Platies or Swordtails. They might not like aggressive tank mates like Cichlids.

One important thing is that Coolie Loaches love hanging out with their own kind! So never buy a single Coolie - always buy 2-3 at the same time. 4 is a good number.

How Long Do Coolie Loaches Live For?

Well this is a bit of a mystery really!

I bought my own Coolie Loaches in 2005, and I'm writing this in 2012. So my fish are at least seven years old! That's a pretty impressive age for a tropical fish to live for, especially in an aquarium environment.

What's more, when I bought my Coolies they were fully grown. So they might even be eight or nine years old! I'm not sure how long Coolie Loaches take to grow. I did once raise some Platies from babies, and I was stunned at how slowly they took to reach adulthood. Baby fish don't grow nearly as quickly as birds do!

By the way, I once looked on the Internet and there seemed to be various extraordinary claims of Coolie Loaches living for 30-40 years. I'm not sure if this is true. But none of my Coolies have ever died, and they have outlived all the other types of fish I've kept, from Guppies to Gouramis to Tetras.

Breeding Coolie Loaches

There have been stories of Coolie Loaches breeding in tropical fish tanks. However, it's not common for them to do so. I think they would only breed in larger tanks, where there are many Coolies for them to congregate with.

It's also pretty hard to tell the males from the females. Females tend to be fatter, but it's much more difficult to sex them than it is fish such as Platies.

So I can highly recommend these little fellows to anyone with a small tropical fish tank. They're the coolest tropical fish you can buy!

Got any questions about Coolie Loaches? Have you already got Coolies in your fish tank? Leave your questions, comments and suggestions below!

Updated: 03/13/2012, brettb
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misty on 12/05/2015

This is incorrect, there are not just two types of loaches. There are many others

seriously on 05/18/2015

The name of the fish is Kuhli. It is named for a German zoologist. Coolie is a racist term for an east asian.

Miriam on 11/05/2012

Will Kuli Loaches eat my baby apistos?

Colleen on 09/07/2012

I have three Kuhlis and one of them is now curved in the middle and cannot straighten out. He can move, but just goes in a circle. It's painful to watch. I've dug around on the web, but can't find anything that explains it's condition. Any suggestions?

Ted Osmond on 08/12/2012

My Kuhli's always float upside down, And my theory to that is they are simple trying to eat. I do belive its a lot easier for them to feast on the microscopic what not since they can't really tilt there head up they are just hardwired to flipping upside down to skim the surface.

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