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Algae Eater Fact Sheet

The fish confusingly called in some countries “the Algae Eater”, Gyrinocheilus aymonieri is also known as “Chinese Algae Eater” and “Indian Algae Eater” although it is not native to India, and there is doubt about whether or not it is native to China. Other names that have been used are “Sucking Loach” and even “Sucking Catfish” (It is not technically a loach or a catfish.)


This fish is native to parts of Cambodia, Laos, Vietnam and Thailand.  It usually lives in flowing water where it will use its sucker mouth to hold onto objects.

Length and Longevity

The Algae Eater can reach 28 cm (11 inches) although I have only seen two of these fish as big as this.  Typically, in an aquarium they will be less than 10 centimetres (4 inches) long.

They can live as long as 15 years.

Water Conditions

This fish needs clean water without a large accumulation of organic waste.  It also needs plenty of Oxygen in the water.

The Algae Eater can take a pH from 6 to 8 and a wide range of hardness.  It is by nature a tropical fish although it can survive cooler conditions than most tropical fish.  In my experience, it can be acclimatized to the temperatures normally found in unheated aquariums in houses with normal levels of general heating, but the acclimatization has to be done very slowly (preferably by putting the fish into the unheated aquarium during summer or autumn when the aquarium is still the same temperature as a heated aquarium and allowing it to cool naturally as the season cools down.)  In fact this fish seems more susceptible to a sudden drop in temperature than most tropical fish.


My customers often ask me if this fish will live in ponds and reduce the algae.  I do not recommend that this fish be put in ponds; except in tropical or near tropical climates.  In the Adelaide Hills of South Australia where I live the water temperature in ponds in the winter will get down to 4 degrees C (39 degrees F).  This is the temperature of fresh water that is under ice.  This is much to cold for Algae Eaters.  Another reason for not using them in ponds, even in summer, is that I doubt if the amount of algae one or two of these fish would eat in a reasonable sized pond would make a noticeable difference to the algae in the pond.

BUT, despite what I have just written, some people have put algae Eaters in ponds in our area.  I would have expected them all to die in the first winter.  However, this does not always happen.  One couple told me of their experience.  They put two of these fish into a pond.  They didn’t see their fish again for two years.  Then they cleaned out the pond, and caught the two magnificent Algae Eaters.  They had not only survived, but had grown to an estimated 12 inches (30 cm) long; the estimate is my own.  They were moving away and were getting rid of all their fish and they brought the two Algae Eaters in to our shop.


As the name “Algae Eater” suggests, they eat algae.  However, the type of algae they eat is green algae so they should not be expected to eat other types of algae.  As well as algae, they eat the many types of organisms that grow on and with algae.  The general name for this type of algae based film of living things is “aufwuchs” which is German for “surface growth.”

Other foods that can be given them include peas and slices of other vegetables as well as Brine Shrimp, Blood Worms and Daphnia.

Although when they are young, algae is their main food, they will eat other things including many common fish foods as well as the special algae wafers that are available.  As the fish get larger, they increasingly eat more meaty foods.


Although the common colour for this fish is a mottled green, there are some commonly available gold or part gold Algae Eaters available.  There have been reports of artificial dying of this fish, but the only gold ones I have seen are not dyed fish, but have been selectively bred for their colour.


Many people, including myself, keep this fish with a very wide range of other fish and it is commonly kept to reduce the algae in community aquariums.

But some individual fish of this species will suck on the sides of mostly larger slow moving fish.  This can be very damaging to these fish and will often lead to their death.  Although even small Algae Eaters will sometimes do this, it is likely to become more of a problem as the Algae Eater becomes larger.  Algae Eaters also become increasingly territorial as they get bigger.

Very large Algae Eaters have been reported to swallow small fish like Neon Tetras.  I have never observed this myself, and would not expect it to happen with the usual size of Algae Eaters we get.

With all the problems associated with this fish, the question might fairly be asked “Why do you sell them?”  At one time I stopped getting them, but my customers wanted me to have them.  They are the most popular algae eating fish.  Personally I prefer the Bristlenose Catfish, but Bristlenose Catfish are not always available and tend to be about twice the cost of the Algae Eater.


The usual small algae Eater we see are too small to show any sex differences.  When they are mature the male can exhibit breeding tubercules on their nose.  The females become fatter.


Although some of our customers have mentioned that they have had young Algae Eaters appear in their tank, information about successful home aquarium spawning of this fish is lacking.

They are bred extensively commercially in ponds in warmer climates.  Sometimes hormones are used to stimulate spawning.

Food Fish

In some countries they are eaten, either as a fish by themselves, or in fish paste, often with a mixture of other fish.

Conservation Status

This fish has not been evaluated for the UICN Redlist, but other sources of information suggest that it is not in immediate danger.

Pest Fish

Avoid allowing this fish to get into waterways in areas it is not native to.

Common Names

The common names used for this fish include ‘the “Siamese Algae Eater”.  This name is very misleading because it leads to confusion with Crossocheilus oblongus which is the fish normally referred to as the Siamese Algae Eater.  Other names that have been used for Gyrinocheilusaymonieri in English include: “Siamese algae-eater”, “Siamese headbreather”, “Sucker Loach” and “Sucking Loa”.

Scientific Names

The accepted scientific name is Gyrinocheilus aymonieri (Tirant, 1883).  Other names which have been used include Gyrinocheilops kaznakoi (Berg, 1906),   Gyrinocheilus kaznakoi (Berg, 1906) , Gyrinocheilus monchadskii (Krasyukova & Gusev, 1987),  and   Psilorhynchus aymonieri (Tirant, 1883).

Algae Eater
Under belly of Algae Eater
Golden Algae Eater
By Gourami Watcher (Own work.) [CC-BY-SA-3.0 ( or GFDL (], via Wikimedia Commons