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Sparkling gourami anabantoid

Air breathing fish, a comprehensive guide to Anabantoids

What are Anabantoid fish?

Perhaps the best introduction to this suborder of fish comes from its own name: Anabantoidei which comes from the Greek word meaning to travel upwards. This is exactly what Anabantoids do: they swim to the water’s surface where they are able to breathe air. I’m sure you’ll agree that the ability to breathe air is a remarkable feature for a fish to have, but that’s not the only thing that makes Anabantoids so very interesting to keep. Here is a comprehensive guide to Anabantoid fish.

Anabantoidei is a suborder of the Perciformes order. Fish in this order are characterised by having ray fins consisting of webbed skin kept in shape by spines or bones. They are distinguished from other suborders by their labyrinth organ.

The labyrinth organ

Sparkling gourami anabantoid

So just how do Anabantoids breathe air? Well, they use a specially adapted part of their body called the labyrinth organ. The labyrinth organ is located just above the gills underneath the gill cover, more scientifically known as the operculum. They labyrinth organ is comparable in both form and function to a lung having a large surface area of vascularised tissue. It extends from the gill arch, a bone used to support the gills. This means that gas exchange can take place in Anabantoid fish allowing them to breathe air and provide their bodies with the oxygen required for respiration.

The photo to the right shows a sparkling gourami with these parts labelled. The sparkling gourami is one of the smaller Anabantoid fish.

Why do they breathe air if they have gills?

Anabantoid fish naturally occur in bodies of water in which oxygen levels are low. Typically these are still or slow moving and relatively shallow, rice fields for example. Labyrinth fish have consequently developed the ability to breathe air in place of relying exclusively upon their gills to provide their oxygen needs.

Labyrinth fish must have access to the water’s surface in order to breathe or they will suffocate; only when the water is saturated with oxygen will they be able to survive without breathing at the surface, however their natural behaviour would probably dictate that they would breathe at the surface regardless. Such conditions rarely occur either in nature or in an aquarium so access to the water’s surface is absolutely essential. Some smaller Anabantoid species do not frequently breathe air with their labyrinth organ, but it’s there should they need it nonetheless. Such specimens are likely to be from less oxygen deprived waters and are therefore also likely to possess relatively smaller labyrinth organs.

Other common appearance characteristics

So now we know that all Anabantoids can breathe air, great, but there are other common characteristics to look out for in these fish: They are generally fairly long compared to their overall size and often have dorsal and pectoral fins reaching the entire length of their body. They often have fairly long caudal fins too.

Paddy fields, anabantoid habitat

© vepasumanth

Habitat

Labyrinth fish are mostly found in tropical areas, with a few exceptions living in subtropical areas in southern Africa and eastern Asia. They are only found in Africa and Asia with no specimens having been found in America. Owing to their ability to breathe air you may have already guessed that their natural habitat consists of marshes and swaps where water is slow moving. This set of parameters occurs mostly in coastal rainforest areas.

Rice paddies provide the perfect habitat for labyrinth fish and, as you would expect, Anabantoids can be found here too. One of the most important fish to inhabit rice paddies from an aquarium owner’s point of view is the Siamese Fighting fish, also known as the Betta fish. Thanks to their air breathing talent and overall hardiness, Anabantoids are often found living in water that’s home to very few other fish species.

Keeping Anabantoids in the aquarium

Whilst Anabantoids share certain characteristics please remember that you must always research individual species and their aquarium requirements before attempting to keep them at home. The majority of Anabantoid fish make good, peaceful community fish however some species, particularly Betta splendens, the betta fish, and Macropodus opercularis, the paradise fish, are some of the most aggressive aquarium fish. Hence why it pays to do your homework before you commit.

Aquarium and water parameters

Anabantoids are kept in both the smallest and largest of aquariums found in the hobby. Betta fish, Betta splendens, are often kept in small bowls and cups as well as paradise fish and other small labyrinth breathers. The labyrinth organ has lead to the misconception that these fish can be kept in badly maintained bowls with no circulation or filtration simply because they can breathe at the surface anyway. This is entirely incorrect as oxygen levels form only one aspect of the overall quality of water in an aquarium as most fishkeepers, novice or expert, should understand.

All Anabantoids should be kept in filtered and heated aquaria and, whilst water movement need not be strong, a decent rate of turnover is still necessary to achieve the necessary biological and mechanical filtration; strong currents can be broken up and diffused using a spray bar or heavy planting.

Aquarium size and stocking numbers

There is no standard size for keeping these fish as there exists such variation in size and requirements amongst Anabantoids. A small 5 gallon tank can keep a betta fish happy whilst giant gourami require something altogether much larger. You can keep several Anabantoids together in the same aquarium, you can even keep them with other fish species providing they are compatible. Nonetheless, you must not assume that peaceful fish can be overstocked as this can still lead to aggression regardless of their habitual temperament.

Given we know that these fish require access to the surface, obstructions that might prevent this should be avoided when selecting a suitable tank.

Water parameters

Please research your species before buying as all have different requirements. Temperature ranges between 22 and 28°C for Anabantoids and they do not suffer from low oxygen levels associated with higher temperatures. Ph should fall between 6 and 8 with no rapid changes. Adding left litter and bogwood will help to emulate their natural habitat as well as releasing tannins that are found in the still bodies of water these fish are naturally inhabit. A wide range of water hardness is accepted by most Anabantoid species as long as this doesn’t fluctuate too quickly.

Plants

A heavily planted aquarium suits Anabantoids and replicated their natural environment. Live plants also form a good habitat for very small organisms eaten by smaller species of fish. Floating plants are ideal if you are trying to breed these fish.

Feeding

Honey gourami anabantoid

© vincent.limshowchen

There is no standard when it comes to feeding Labyrinth fish; most are carnivorous with very few accepting plant based food, such as the giant gourami. Depending upon what they are fed, there are some interesting observations that can be made of Anabantoid feeding methods.

Skimming

The fish swims to the surface and gulps in water from the surface, filtering out small food particles left floating on the surface.

Grazing

This involves foraging around algae and other fine plants in order to find small, microscopic in fact, organisms to eat.

Biting

As simple as that, take aim and bite. This is the method most often used when you feed flakes to your fish.

Spitting

A highly complex calculation, the fish takes aim at prey above the water surface and spits a small amount of water in the hope of knocking them out of the sky and into the water where they are quickly consumed. The fish must take into consideration the refraction that occurs between the water and air, something they may have evolved or learned to do, but still representing a good deal of intelligence.

Jumping

Like many fish, Anabantoids can jump out of the water in order to catch small flying prey, usually flies.

Betta fish are also anabantoids

© Tanakawho

Fighting

Putting aside the famous Siamese fighting fish, Betta splendens, there is a possibility for all labyrinth fish to become very aggressive and use anything up to and including lethal force against other specimens. The probability of violence increases with proximity to a spawning period during which males in particular are keen to protect their eggs and establish their territory.

Before engaging in fisticuffs, many Anabantoids, especially Bettas, flare up their fins and puff out their operculums attempting to intimidate their adversary. Failing this, their next step is to adopt an aggressive stance, blocking their opponent’s way and showing off their fins as much as possible. Other Anabantoids such as the climbing perch face each other head on. Other aggressive manoeuvres such as tail nipping also ensue if no resolution is found with less violent measures.

It is important to limit such aggression in the aquarium as fin nipping can lead to secondary problems such as infections. In some rare cases, usually in small aquariums, fish have been known to have lost almost all of their fins in such vicious attacks. In the wild there is much more space to retreat making this kind of behaviour less common. In some countries betta fish fighting is considered a sport with huge sums of money bet on the outcome.

Upon having built a bubble nest, which is explained in further detail in the breeding section of this guide, males will chase anything that dares come too close. This is the most aggressive stage of keeping these fish; even the female is only allowed in the next for a brief period, after which she too is thrown out with charmless aggression. In the confines of a small aquarium, many females find themselves unable to escape the male, resulting in severe injury and sometimes death.

Reproduction

Fertilisation of all Anabantoid eggs occurs outside of the fish, usually underneath a bubble nest, a structure of bubbles created by the male from saliva and water. Anabantoids produce pelagic eggs meaning they float and need to be protected by the bubble nest to ensure that they aren’t preyed upon or carried away.

When mating, Anabantoids will come close together, often wrapping around each other to ensure their genitals are as close together as possible. This ensures that fertilisation occurs before sperm cells die off. After mating, some males tend to their eggs, and young fry, whilst others are mouth brooders meaning they carry their eggs around in their mouths to ensure their well-being.

And there you have it

They breathe air, shoot flies out of the sky and perform some truly amazing fighting rituals. These fish are incredibly interesting and make great additions to any aquarium. This guide has dealt with Anabantoids on the whole and further research must be carried out before keeping any species of this order of fish.

 

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