Kribensis

kribensis-breeding-pair-guarding-nest

kribensis-pair-with-young

Kribensis : Everything you need to know

Kribensis (Pelvicachromis pulcher) inhabits a range from Benin, into Nigeria and Cameroon, but mostly Nigeria..
It was first introduced into the hobby in the 1950s and immediately became a big hit with aquarists.

In the wild kribensis breed in the side of river banks by digging away soil between roots to create a cave. Wild kribensis live on the riverbed between roots and leaves.

Feeding kribensis

kribensis-feeding
kribensis-feeding

Kribensis are omnivorous, eating a mix of animal food and vegetable matter. Algae is good for them.
In the aquarium they readily eat flake or dried food with ease, but the occasional piece of veggie matter such as cucumber slice or lettuce or even algae is relished. Live food can be used to prime them when you want to start breeding them.

To get the best from your kribensis supplement their diet with plenty of fresh greenery such as blanched spinach and dandelion, flaked pea, and any of the seaweed products frequently marketed for marine keepers.

Kribensis behaviour

kribensis pair guarding cave
kribensis pair guarding cave

Kribensis are a little shy and need peaceful dither fish. They also need lots of hiding places such as caves made from clay pots or half coconut shells and plants to make them feel safe. This will encourage them to come out so you can see more of them.

Although kribensis are mostly found in rivers, they do not like a fast water flow. That is explained by the fact they inhabit the bottom of the river on the river bed amongst roots, rocks and caves where the waterflow is very slow. They a good knowledge of their surroundings, which means it is better to not change the aquarium set up as this unsettles them.

Kribensis Description

kribensis-female-breeding-colours
kribensis-female-breeding-colours

Male kribensis are larger than females. In the aquarium the biggest males are about 4 inches and the biggest females about 3 inches. In the wild specimens have been found just under 5 inches long.

Males are long with a gently curved underneath from head to tail. Females are stubbier with a rounded red/purple belly. Males might have a red/pink patch near the throat

Female kribensis fins are rounded while kribensis males fins have longer and pointed fins.

Kribensis Colour

kribensis male in breeding colours
kribensis male in breeding colours

Kribensis have a black/dark stripe on a creamy background running along the side and another dark stripe on their backs that extends into a dark dorsal fin edged in yellow. Both males and females have blue in their pectoral fins and other lower fins, especially when they are breeding. Females become more yellow especially above the stripe when they are breeding. Most kribensis have an eye spot in the top of the tail fin and at the rear of the dorsal fin. Some male kribs have multiple eye spots in the tail fin.

When in breeding mood the area between the red belly and the tail darkens on the female. This accentuates the females red/purple belly.

Water conditions for kribensis

They like slightly acid and soft water from the wild but most aquarists keep them in neutral ph water. Because of the

kribensis-for-sale-in-shop
kribensis-for-sale-in-shop

long time that kribensis have been kept and bred in captivity with few wild specimens coming through, they have become adapted to a wide range of waters conditions. They are capable of breeding in a wide range of ph values.
The temperature ideally should be at 77F but kribensis are happy any where between 75-80F

How and where to buy kribensis

A good place to buy is from online sources such as gumtree, aquarist classified, craiglist from a private breeder. You can also buy from your local aquarium store. Be wary of buying from your large pet chain which will usually have untrained staff. Remember young fish will have less colour than more mature fish so they might have disappointing colours when you buy.

Check all your different sources for buying fish and try to buy from two or three sources a few fish each to give a better genetic mix for your fish.

Do not just choose the largest fish from a brood or you will end up with just males. Sometimes you can tell males and females by body shape when the young are larger but smaller fish you can’t really tell so size is a reasonable indicator.

Kribensis tank set ups

Kribensis cichlids can be kept and even bred in a community aquarium, a species aquarium or even in a West African biotope aquarium

kribensis-community-aquarium
kribensis-community-aquarium

Kribensis in the community aquarium

Make sure you don’t get fish that out compete them for food. With Kribs being bottom feeders, they usually wait until the food goes lower before eating especially. It is best to avoid tankmates that snap up their food near the surface before the kribensis get a chance to feed. This is most noticeable when the kribensis are small and hide a lot.

Kribensis rely on dither fish such as a school of small tetras to tell them whether it is safe to wander out of hiding. A few peaceful dither fish will encourage them to come out and explore instead of hiding so that you get to see them and admire their beauty.

Avoid other bottom feeders such as catfish which will disturb the kribensis, especially when they are breeding.

Kribensis species aquarium

kribensis-west-african-biotope-aquarium
kribensis-west-african-biotope-aquarium

Having a tank of just kribensis can come about if you have had a breeding pair and kept all the offspring. The tank must be quite large at least 160 litres. You need to kit it out with plants, dark sand and many cave like structures such as half coconut shells or half clay pots. The kribensis males will form harems, dispelling the myth that kribensis form monogamous relationships.

Kribensis biotope aquarium

If planning on biotope, then sand, branches and cobbles are the prime choice of décor. For planting, provide opulent growth. Tangles of Crinum species and banks of Cyperus, Ceratophyllum and Ceratopteris, plus ample Anubias and Bolbitis fastened to the wood will provide abundant cover.
For authentic fish, think of Brycinus longipinnis tetra, and Pareutropius buffei catfish. Aphyosemion gulare killifish are abundant in the same areas as kribensis and make a pleasing enough companion. Also jewel cichlids are found in kribensis territory in West Africa

kribensis-breeding-tank
kribensis-breeding-tank

Kribensis breeding set up

-24/30in long aquarium
-heater
-2 x mature sponge filters
-2 or 3 half clay pots or half coconut shells
-plants unlike other cichlids they are not great plant uprooters. However they may nibble on plants.
-driftwood
-rounded stones
-dark sand substrate or very fine dark gravel
-low wattage light to provide dim lighting at night

Preparation for breeding kribs

kribensis-eating-live-food
kribensis-eating-live-food

Buy 6 or more young kribs. Be careful to not just buy the larger fish in the tank as these are usually males. Remove any other bottom dwelling fish from the aquarium such as catfish. Kribensis prefer soft neutral water but can breed in a wide variety of water conditions. So just keep the aquarium water parameters stable and clean. Note: Higher ph tends to increase the ratio of females to males born whereas lower ph gives you more male to female offspring.

Prime the pair by feeding plenty of live foods including chopped earthworms. Keep the temperature at about 76F. If they fail to start breeding then raise the temperature a couple of degrees to encourage breeding but not go higher than 80F

kribensis-female-displaying-to-male-2
kribensis-female-displaying-to-male

Kribensis breeding behaviour

Kribensis can become very territorial when breeding and caring for young so be careful of other inhabitants. The female’s red belly will become solid red/purple. The top of her body between the dark stripes will become yellow. Her throat will also become yellow. Both fish will develop bluish pectoral and ventral fins and they will also develop a blue edge to the gill plate.

The female will bend her body sideways exposing her red belly to the male. If he is interested he will follow her to the breeding cave. They will then go through a ritual of shimmying behaviour to each other. They will

kribensis-pair-cleaning-nest
kribensis-pair-cleaning-nest

then take it in turns to go into the cave and come out again possibly spitting out some substrate outside the cave. This mimics the behaviour in the wild where they dig holes in the soil at the side of the river to create a cave. Each time they come out they will shimmy to each other.

Kribensis females usually lay about 200 eggs. Young kribensis mothers lay less eggs.

The female will usually lay her eggs on the roof of a cave but sometimes they are laid on the floor if it is suitable. The eggs are large and adhesive so stick to the cave wall. The female mouths them to keep them clean until they hatch. She will not leave her cave until they hatch. They hatch after 3 days and the fry will not become free-swimming until after another 7 days. Do not feed the fry until they become free-swimming.

Raising the kribensis fry

kribensis mother guarding her brood
kribensis mother guarding her brood

Kribensis parents co-operate in protecting the eggs and herding the young. The female will usually be closer to the young while the male will skirt around the perimeter protecting from threats.

In the wild kribensis are known to co-opt other kribensis fry into their own brood. It is thought to raise the survival rate of the baby kribs. The reason could be safety in numbers and as a backup for stray fry.

Harmless dither fish can help the parents to co-operate in looking after their brood. The parenting kribensis will focus their attention on protecting their fry from an external threat rather than considering each other as a threat.

Sometime, however one parent might get nervous of the other parent and push her/him away especially if there are no other fish in the aquarium. This is usually the male that is seen as a threat but sometimes the female will be pushed out. It is best to remove the harassed parent from the tank.

To protect the male(or female) from the overprotective parent then provide plenty of hiding places and a bigger aquarium. This should keep them safe. You could also consider moving him/her to another tank if the bullying gets too much.

kribensis-pair-guarding-eggs
kribensis-pair-guarding-eggs

Surprisingly for such a small fish, they lay quite large eggs and when the fry hatch they are quite large and can eat brine shrimp from birth. This makes raising the fry a lot easier for the beginner. The fry also pick at microscopic life forms growing on algae growths on the glass and on sponge filters.

keep a low wattage night light on so that the parents can protect the fry especially if there are other fish in the aquarium. Daily water changes of 5% and having many plants will keep the nitrate levels down.

As the fry grow you can start feeding flake food. You will also need to thin out the brood by selling on the young or moving them to another tank, depending on how many young fish you have.

Relatives of the kribensis

Most Pelvicachromis are readily bred in the aquarium. Breeding behaviour and care is similar to P.pulcher.

pelvicachromis-taeniatis-male-female
pelvicachromis-taeniatis-male-female
Pelvicachromis taeniatus

Historically this was the original kribensis but has been replaced by the popularity of pelvicachromis pulcher. There are many colour variations and patterns in males of all species of Pelvicachromis, Several populations of each species appear to co-exist in different regions. Pelvicachromis taeniatus are sometimes offered with names hinting to which region they were caught from. You might see P. taeniatus ‘Nyete’ or ‘Moliwe’ which will differ substantially to P. taeniatus ‘Niger red’.

Pelvicachromis subocellatus
pelvicachromis-subocellatus-male-female
pelvicachromis-subocellatus-male-female

The males are less colourful than normal kribs but the females are quite interestingly coloured having a dark collar between the head and the red belly and another dark area the other side of the red belly. The tails have a yellowish net pattern in them.

Other “kribensis species from the Pelvicachromis family include:

  • Pelvicachromis drachenfelsi
  • Pelvicachromis kribensis
  • Pelvicachromis roloffi
  • Pelvicachromis silviae
  • Pelvicachromis sacrimontis

There is also an albino version of the kribensis that is not a true albino and does not breed true. The albino will have pink eyes and a mostly white body but the female will still have the red belly. Both male and female will have yellow edging to the fins.

Goodeid Fish

male xenotoca eiseni

(A different kind of livebearer)

ameca splendens

What Are Goodied Fish?

The Goodeidae family is an interesting group of fish. Sadly, some of the subspecies are becoming rarer and rarer in the wild and are even thought to be near extinction. The range of their natural habitat is represented by the shallow waters in central Mexico, and they are also present in parts of the Great Basin, of the US. Since this type of fish has no economic importance, efforts to promote conservation has been lacking.
If you decide to keep these fish as pets, you will have to learn a few important things about their particular needs. Unlike other fish, these are livebearers, which means that the female becomes pregnant, in a similar way to mammals. Live-bearing species of fish can be quite different than others, which is why you should pay extra attention to their living conditions and overall care.

About the Goodied fish

La Luz Splitfin goodeid fish
La Luz Splitfin goodeid fish

A large family of fish native to Mexico and the south east part of the USA, the Goodied has 40 species. They are popularly known as splitfins, due to a physical characteristic noticeable in males. They can be as large as 8 inches, but most subspecies are smaller, growing up to 2-3 inches in length.
As live-bearers, the Goodied females support their fry inside their body until giving birth, and there is a connection that allows the feeding of the young, very similar to the umbilical cord in humans. Each fry is fed throughout gestation in this manner. With each pregnancy, one female can produce around 10-15 fry, with smaller numbers in some species and higher numbers in others. There are differences in their behavior towards their young, too. While some species prey on their fry, others do not.

Splitfins do well in milder temperatures, around 70F. They prefer harder, more alkaline water, and, in general, they are not fussy eaters.

Many species of Goodied are threatened with extinction. For instance, the bluetail splitfin, the rainbow characodon, the relict splitfin, the Allotoca diazi and the Manse Spring killifish are endangered, while the butterfly splitfin and the golden skiffia are already extinct in their natural environment.

male ilyodon xantusi
male ilyodon xantusi

The most important sub-families of Goodied are: the Allodontichthys, the Alloophorus, the Allotoca, the Ameca, the Ataeniobius, the Chapalichthys, the Characodon, the Girardinichthys, the Goodea, the Hubbsina, the Ilyodon, the Skiffia, the Xenoophorus, the Xenotaenia, the Xenotoca and the Zoogoneticus.

The Goodied do well in aquariums, and while they demand some care and special attention, they are not extremely difficult to breed and take care of.

Since you may be wondering what kind of Goodied fish you should bring home, I will talk to you mostly about the two most popular types: Ameca Splendens and Xenotoca Eiseni.

Ameca Splendens

Appearance of Ameca Splendens

ameca splendens species aquarium
ameca splendens species aquarium

Better known as the butterfly splitfin, the Ameca Splendens is a beautiful looking fish. You will be able to tell a dominant male from the rest by its over-sized dorsal fin that is streaked with black. A yellow stripe that stretches towards the tail is another characteristic of males that makes them stand apart. The body has an ochre color, with silver shades on the sides, and brown tones on the back. The males tend to look fancier than females with their metallic scales that tend to glitter when there is little light. You will recognize females and the young by their black dots on the fins and the sides. An interesting fact about the male butterfly splitfin is that he can modify his color intensity depending on his mood.

Males can grow up to 3 inches, while females tend to be larger, growing up to 4 inches, when provided with good living conditions.

Aquarium conditions

If you are interested in keeping this species of fish in your tank, consider getting a 30-gallon aquarium. These fish thrive in water conditions that vary between 70-78F, and the desired pH levels should be 7.0-8.0. Water hardness can go towards the extreme high end of the scale, and more than 10.5gpg is recommended.

They love hiding among plants, so a densely populated aquarium is a good choice for the Ameca Splendens. Bare bottomed aquariums are particularly loved by this fish. If you provide moderate lighting you should get an aesthetically pleasing effect, as the beautiful coloring of both males and females will be more striking on a darker substrate. Keep in mind that this type of fish does not tolerate poor water quality, so good filtration is needed. Moderate water flow is your best bet, as far as further conditions are concerned.

What does Ameca Splendens like to eat?

It can be safely said that the butterfly splitfin is quite a greedy eater, which means that it is not fussy about what it is fed. Nonetheless, you should focus on providing a varied enough diet. Algae are most preferred, but spirulina flakes and dried seaweed make for nice treats. Speaking of treats, live food, such as daphnia and brine shrimp, should be included from time to time.

Are they aggressive?

When kept in a community of Ameca Splendens, they are not usually aggressive, but the strongest males and females may tend to bully others from time to time, although without going to extremes. However, you should keep in mind that they tend to be quite competitive when it comes to feeding, so, if you are planning on placing them together with other fish, choose more robust species that are not easily bullied by the boisterous behaviour of the butterfly splitfin.

The strongest alpha male can be noticed by his bright coloring and slightly larger size. While they may establish a pecking order inside a tank, the males do not get particularly aggressive, and serious damage seldom happens. This is a species that does not eat its fry.

Breeding recommendations

You can multiply your beautiful butterfly goodied fish by using just one pair, or more, if you prefer. As live-bearers, they tend to be particular when it comes to their breeding habits. The mating ritual is initiated by females, and males increase their coloring as the courtship begins.

Females are pregnant for 55 to 60 days and they can give birth to between 5 and 30 fry that can be quite large up to 0.75 inches in length. Their large size from birth allows the fry to feed just like adult fish and they are not usually preyed on by the others.

One thing to keep in mind is that you should prepare the tank for the breeding and the pregnancy period in advance. Females are known to be easily disturbed if they get moved while in gestation. The stress of being moved usually causes the female to suffer an abortion and even die. I recommend the use of a large breeder net in the same tank, to avoid upsetting the females.

Xenotoca Eiseni

Appearance

male xenotoca eiseni
male xenotoca eiseni

Going by the name of the redtail splitfin, Xenotoca Eiseni is another beautiful subspecies of the Goodeidae family. You can tell the males apart from the females and the young by the large hump behind their heads. This hump grows with the fish, so older males are easy to notice because of these large humps. Another thing that makes the males recognizable is the blue coloring of the body, and the red or orange coloring of the tail and penduncular area. As is the case with other live-bearing species, the females tend to exhibit less noticeable colors and a larger size.

Males can grow as long as 2.4 inches, while the females can grow up to 2.8 inches, being slightly larger.

Aquarium conditions

male xenotoca eiseni
male xenotoca eiseni

The redtail splitfin is not particularly needy or demanding when it comes to aquarium conditions. It can tolerate colder temperatures, and it does well within the 59-80F range without a problem. Smaller than other species, they do not require a lot of room to swim around, so they will have no issue living in a 10 gallon tank. However, if you are planning on starting a colony, consider getting a larger tank, up to 29 gallons.

The water pH levels this fish can tolerate vary between 6.0 and 8.0. Hard water, more alkaline, is what they prefer, and keep in mind to avoid keeping them in water over 75F. Consider a tank with a dark substrate, to allow the goodeid fish to exhibit their beautiful colors to the full.

What does it like to eat?

It is good to know that this fish is not a picky eater. It is omnivorous and it does well on any kind of diet. Don’t forget that plants must be part of a daily diet, nonetheless.

Are they aggressive?

Although they are so small, compared to other species, they tend to be a bit difficult when placed in a tank with other breeds. In particular, you should know that the redtail splitfin does not get along with catfish, for which manifests a strong aversion. Stripping the fins and attacking other species like Corydoras are not unlikely events, so I recommend considering a species aquarium just for them. They are also known to prey on their fry.

Breeding recommendations

female xenotoca eiseni giving birth
female xenotoca eiseni giving birth

If you are planning on starting a colony, you should keep in mind that this species preys on its young. You can prevent such behavior, by heavily stocking your tank with more plants, so that fry can hide. Also, offer them enough food, so that the most aggressive individuals have less reason to eat the young.

The gestation period for females is 60 days and they can produce 5 to 15 fry in one pregnancy. From the start, the fry can consume the same type of food as their parents. In a well planted aquarium, the redtail splitfin produces more fry than what it can prey on, so over time expect to see their numbers multiply.

You could also remove all the other fish from the females aquarium leaving the lone female to give birth without the risk of the fry being eaten by the other fish. After the female has finished giving birth, you should remove her as well. Then the fry can be raised without any risk of being eaten.

Fish anatomy

fish anatomy

River fish are usually streamlined

Anatomy of fish

The shape of a fish’s body tells you a lot about its behaviour in the wild. Long stream-lined fish are usually lake or river fish. Being streamlined helps a fish to swim faster in rapid moving waters or open bodies of water such as a large lake. Short or stocky fish are usually from ponds or live near the bed of a river. Side flattened fish usually reside in in slow moving waters with lots of vegatation or roots. The body shape helps these fish swim between plants and reeds. Top flattened fish usually swim on or near the river bed or floor of a pond. Fish with mouth barbels usually swim near the floor of the river or pond and use these barbels to seek food on the murky bottom.

Mouth Anatomy of fish

The shape of a fish’s mouth tells you which part of the water it feeds from. Fish with upturned mouths feed from the water’s surface. Fish with forward pointing mouths feed mostly from midwater. Fish with down pointing mouths feed near the pond floor or river bed. Fish with mouths underneath the head feed off the floor or off algae attached to encrusted rocks.

Fish scales

The scales on a fish’s body provides physical protection from injury. These scales are quite tough and overlap each other to form a tough but flexible armour. The whole of the fish’s scaly body and fins and all body parts are covered in a slimy mucous. This mucous is being continuously secreted by the fish and is used to wash away any bacteria, fungus or virus from invading the body of the fish.

Fins of fish

Fins are used by fish for propulsion, steering, stability and braking. Fins have a secondary function as flags and signals to other fish. Fins when held spread are usually a sign that the fish is healthy, while a fish that is unhealthy will tend to clamp its fins closed.
Some fins are single while other fins are paired. All fins have some purpose.

The single (unpaired) fins are:

  • Dorsal fin – This fin is used for stability
  • Tail fin – This together with the tail is the main means of forward propulsion
  • Anal fin – This is used for stability and in male livebearers is adapted into a reproductive organ.
  • Adipose fin – This is found in some species such as the characins or tetras. This fin appears on the top of the fish in between the dorsal fin and the tail fin.

The doubled fins

  • Pectoral fins – Pectoral fins lie on either side of the body behind the gills and are attached near the bottom of the fish’s body. They are used for braking, manoeuvring and reversing.
  • Pelvic fins – These lie forward of the fishes anus. On most fish these are attched mid body near the bottom of the fish’s body. The pelvic fins helps the fish to rise and descend through the water. They also help the fish turn sharply and assist braking.

Swim Bladder

The swim bladder in fish is an air filled sac that is within the fish’s body that aids in buoyancy and maintaining the fish’s level in the water. By relaxing or contracting the muscles of the swim bladder a fish can compress the air sac or expand the air sac. When the fish decides to compress the swim bladder it will sink. When the fish expands the swim bladder it will float.

Fish Senses

Fish have the same five senses we humans have, plus they also have a specialised sixth sense, the lateral line. The lateral line runs along the middle of the fish from begind the gills to the tail on both sides. The lateral line consists of small pits in the middle of each midline scale. The water filled pits contain small neuromasts which are minute finger shaped structures that contain hairs. When currents enter the pits the neuromasts move, sending a nerve signal to the brain of the fish. This detection of minute changes in flow and water pressure allows the fish to sense its surroundings in a sonar like way. This sense is used in shoaling and detecting minute water currents from prey, other fish or objects. Blind cave fish rely on the lateral line to ‘see’.

Sense of taste in fish

Of course fish don’t have tongues but they do have taste buds in and around their mouths. Many fish also have taste buds all over their body. Many bottom feeding fish have taste buds in their barbels.

Sense of smell in fish

Fish smell through their nostrils. Some fish have two sets of nostrils that allows water to flow through them. Water is pumped into the intake nostril and expelled out of the ottake nostril. The resulting flow of water that passes across receptor cells in the nostril cavity which detects chemical messages and sends signals to the fish’s brain. Fish use their sense of smell to swim away from some smells that may be harmful, such as that of a predator. Or they may swim towards a smell of food or towards potential mate.

Sense of hearing in fish

Although fish do not have ears they do have an internal ear mechanism. Sound actually travels faster through water than through air. Sound travels through water as a series of vibrations. These vibrations travel through the fish’s body mostly undisturbed. However in the fish’s inner ear there are tiny bones called otoliths. Because the otoliths are denser than the surrounding flesh, they vibrate. This vibration is detected by nerves attached to these bones. The nerves then send signals to the brain. In some species sound is amplified by the use of the fish’s swim bladder.
Some fish can make sounds by grinding their teeth or drumming their swim bladder.

Sense of sight in fish

Sight is an important sense for fish as light does penetrate to beneath the waters surface. The eyes of fish have much in common with amphibians, reptiles, birds and mammals. Fish’s eyes tend to be more spherical though. Most species have colour vision and some fish can even see ultraviolet light. Fish focus their vision by moving the lense closer or further from the retina. Most fish do not have binocular vision. However, the hammerhead shark does have a good binocular vision because it has its eyes set far apart but focussed forward.

Sense of touch in fish

Fish do have a sense of touch that spans through their who skin. Scaleless fish such as some catfish have an even better sense of touch.

Fish adaptation in the wild

Nothobranchius rachovi. Killifish have adapted to extreme conditions.

Fish adaption in the wild

The mudskipper can walk on land using its front fins as legs
Mudskipper walking on land on its front fins

Fish as a group are one of nature’s success stories. Fish can be found in nearly all bodies of water and on occasion can be found flopping onto land. Even the most inhospitable bodies of water such as suphurous thermal springs, ponds that dry up in summer, the deepest part of the ocean have all been colonised by fish.

It is estimated that there are currently 30,000 different species of fish on earth. That is more than any other vertebrate. There are thousands of species that live in freshwater tropical streams, rivers, ponds and lakes. The most abundant of these are in Africa, Asia and the Americas.

The most popular species of fish from these bodies of water have found their way into the aquarium trade and into people’s homes the world over. The most popular species in the hobby are usually the most colourful, hardy and easiest to breed or they may have an unusual shape or unusual behaviour.
Adapting to life

Salmon after 2-3 years at sea swim up river to breed
Salmon after years at sea swim up river to breed

Fish have been on earth longer than reptiles, amphibians, birds and mammals, all of which have evolved from fish. It shouldn’t come as a surprise to note that fish have had longer to adapt to their environment than the other groups of animals listed. They are better adapted to their aquatic environment than most other life forms. They have found their way into many niches and developed many unusual behaviours that better allow them to cope with their environment.

Adaptation to life in rivers

The upper parts of river have fast flowing turbulent waters with little mineral content. The fish that live in these waters have adapted by becoming streamlined and fast swimmers and are able to mainatin a stationary position relative to the river bed while water flows past them. Because of the noise from the turbulent waters these fish have developed better eye-sight and lesser hearing ability. These adaptations help predator fish to better hunt their prey and also helps fish to avoid predation by larger fish and other predators.

Discus with flattened sides and vertical stripes
Discus with flattened sides and vertical stripes

Mid river, further downstream, is where the flow of the river is less and the river widens. Fish found in this part of the river are usually deeper bodied and less stream lined. Water in this part of the river is usually clear which aids fish with good eyesight.

In the river low lands the river becomes even slower and even wider. The water is usually cloudy with dissolved decaying vegetable matter and tannins from submerged logs, pieces of wood and roots.

Because of the water cloudiness in this part of the river fish cannot rely so much on their eyesight. They instead have developed better sense of smell, taste and hearing. Many shoaling fish in this part of the river have developed bright or even reflective scales to enable them to see each other in the murkiness.

Adaptation to life in ponds

There are other tropical fish that have adapted to live in lakes and ponds of Asia. During the hot and dry seasons the ponds and small ditches evaporate and reduce to small and stagnant bodies of water. Gouramis are a class of fish that have adapted to these low oxygen conditions by developing the ability to breathe air. They achieve this by gulping air into a specially adapted labyrinthian organ that absorbs the swallowed air. This allows them to survive in low oxygen conditions that would drown normal tropical fish.
These ponds and lakes are usually muddy or cloudy so having good eyesight is not such an advantage. Fish in these cloudy conditions have developed barbels near their mouth to help them find food. The gouramis have developed a pair of thin hair like fins that they use to feel and taste their surroundings and help them find their way through the thick vegetation. Fish in these cloudy conditions have also developed a better sense of smell.

How fish behave in the wild

Watching a large shoal of cardinal tetras is an enchanting experience

Fish Behaviour in the wild

Fish’s behaviour is affected by the rythms of nature. Fish recognise dawn and dusk and behave appropriately. Fish also recognise the seasons and will mate at the correct time of year that is best suited for the hatching and growth of their young. Fish will go into hibernation at the onset of winter.

Most fish are active during the day and rest during the night. At the break of dawn the fish will be most hungry and active in search of food in the shallows for the first couple of hours of the morning. After they have had their fill of breakfast then they retire to safer, deeper and more reclusive spots in the lake or river.

Young fish tend to congregate in the shallows for 3 reasons

      1. Food is more abundant in the shallows

      2. The sun heats the shallows and fish grow faster in warmer water

      3. Large fish avoid the shallows

Young fish have dull colours such as grey,brown or green that makes them invisible on the muddy banks between the plants and amongst the algae. This helps them avoid being eaten by adult fish.

How do Fish sleep?

Fish will slow down their metabolism, sink to the bottom in a safe spot while remaining relatively motionless. They do not close their eyes because they have no eyelid. It is though that they turn off most of their senses while mainting their lateral line sense active. Any disturbance and with a flick of their tail fin they will dart off to safety.

Some parental fish don’t sleep when guarding their nest of eggs or fry. They remain alert all night and fan the eggs and guard the young from predators.

Fish feeding behaviour

When a fish finds a good source of food it gets excited and starts to gulp the food down. Other fish will notice the excitement and will also get excited and swim towards the food. A feeding frenzy follows where more and more nearby fish notice the commotion and head towards it. All the fish will try and gulp down as much food as possible as quick as possible before the other fish finish it off.

Fish generally swallow their food whole and don’t chew much of it at all. But they will sometimes a bite at a piece of food that is too big and wriggle about until a piece snaps off.

They swallow food by expanding their throat pouch, which has the effect of creating a suction, where food just in front of them will be sucked up into their mouth along with some water. When the food is inside the mouth, the fish will close its mouth trapping the food inside. The fish will expel the excess water through its gills while keeping the food trapped in its mouth. The fish will then taste the food. If the food is stale or inedible the fish will expel the food from its mouth.

Teeth of fish

Most fish are omnivores which means they eat both vegetable matter and living food such as insects and other fish. Omnivores have peg shaped teeth that enable the fish to bite and hold onto its food. Some fish specialise in eating algae. These fish have specically adapted teeth that are flattened into a shape making them ideal fro rasping out algae attached to rocks.

Predator fish have sharp backward pointing teeth that can pierce the flesh of other fish and sometimes scissor together to slice through the flesh allowing the fish to bite off chunks.

Fish sometimes have specialise pharyngal teeth based in the roof of a fish’s mouth. These teeth workin in combination with a fish’s tongue to provide an additional mechanism to allow the fish to grip its food.

Some fish feed on hard shelled creatures such as snails, shrimps or molluscs. They have specialised teeth that enable them to crush or crack open snails shells by use of their pharyngal teeth while biting hard using powerful jaw muscles.

Many bottom feeding fish sift through the sediment at the bottom of the pond or river bed. The sediment contains decaying organic matter where worms and insects grow. Bottom feeders feed off these creatures as well as broken off bits of flesh and plants.

Some fish are mostly vegetarian so feed off the leaves of plants and maybe snatches of algae. These types of fish are hungry fish and generally will eat throughout the day because weight for weight plant matter holds less protein and calories than animal matter.

Coordination of swimming in fish

About half the know species of fish swim about in groups. There are two methods that this achieved

  1. How fish school

Schooling is where the fish of the group swim together in a tightly knitted coordinated way keeping a set distance apart from each other while trying to swim at the same speed and direcdtion as its neighbour. When a lead fish turns its neighbour will turn which in turn leads to its neighbour turning. This is done so fast that it looks like all the fish turn at the same time. This coordinated effect of many fish is called the Trafalgar effect. Schooling is said to provide protection from predators because of a predators inability to focus on a single fish and having multiple confusing targets.

  1. How fish shoal

However, shoaling is when fish swim together in loose groups but without coordinated swimming behaviour. This behaviour is exhibited by social fish. Each fish will try and keep within social distance of other fish in its group. When a threat comes close to the group the group will scatter away from each other and will only re-group when the threat has gone.

Each fish in a shoal has a personal space that it tries to maintain most of the time. In fast currents the shoal will tighten and the fish will swim closer together than in slow or still water where the fish will be in a shoal but further from each other.

Most fish are social animals as can be witnessed by their shoaling behavior. Fish keep tabs on each other by use of sight, smell and use of the lateral line sense.

Members of a shoal tend to be the same size and nearly always of the same species. Any sick or small fish are shunned and excluded from the shoal.

Fish aggression

Fish will fight over food, territory and mates.

Male fish will fight more aggressively to win a mate than they would fight over food. Males usually fight to defend a territory so when the time comes the fish can attract a female to its patch to mate with. Some species will defend a territory around its nest after breeding. They will defend the nest of eggs or young fish from predators. This is when the parents are at their most aggressive. They can kill other fish that are curious and come close to the nest. In some species it is just the male that will guard while in other species both parents will guard.

The largest, strongest or even the most aggressive fish will be the most dominant and will get the best and biggest territory. There is a pecking order of fish from the largest most dominant down to the weakest, smallest fish. Once the pecking order is established fish then tend to not fight each other. Sub dominant fish will give way to more dominant fish. When a new fish turns up in an area fighting will break out between the new fish and the settled fish. The new fish will start out quite low in the pecking order and will over the following days or weeks fight its way up the pecking order until it finds its natural place in the pecking order.

The best breeding territories are defended by the most dominant males. These areas are surrounded by smaller and not so good territories occupied and defended by less dominant males. Further out in smaller and least good territories the weakest males will try to defend their small patch too. These territories border each other with no buffer zone. Border disputes occasionally occur but quickly resolve themselves. The fish do not chase after neighbouring fish by following a neighbour because they would leave their own territory unguarded.

When a female who comes along and is in mating mood she will usualy go the the male with the best territory. All the fish will try to entice the female to their territory by displaying frantically. Only occasionally will she mate with a subordinate male.