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Fish Spawning: An Overview
08 January 2020
No matter how long an aquarist has been keeping fish, there are certain landmarks that stand out in the memory. Even when the first tank and the fish in it are long gone, everyone remembers their first aquarium and their first fish; days of spending hours gazing into the tank, alternately admiring the fish with a sense of pride and staring at them with a hint of panic – is that a tuft of fungus? Is another fish swimming oddly? And then, for most of us, the first aquarium disaster – new tank syndrome, buying a new, un-quarantined fish that spread disease, or any of the other horrors that can overtake an aquarium.
Another memory which stands out clearly for most aquarists – the first fish to spawn or give birth. For some it may have been the culmination of careful and deliberate effort – choosing and conditioning the parents, setting up the spawning tank, while for others it may have simply happened in the community tank. Whether the first fry were planned for or arrived unexpectedly, they are still something special for a fishkeeper – a confirmation that we are doing most things right and that our fish are healthy and happy. For many people this is the start of a lifetime project – the species of fish may change, and we may progress to more difficult (or fussy) specimens, but there is always delight in seeing the first tiny fry swimming around.
Part of the pleasure in fish breeding lies in the fact that often their spawning behaviour is fascinating to watch. Often fish change colour, and are only seen in their ‘Sunday best’ when preparing to start a family. There is also a whole range of behaviours that are only seen as a prelude to, and sometimes a consequence of, spawning. In general, fish fall into one of four categories of breeding methods and behaviours:
Egg scatterers- where the eggs are produced, fertilised, and forgotten
Egg guarders- where one of the parents protects and cares for the eggs
Livebearers- where the fish give birth to fully formed little fish instead of eggs
Family care- where one or both of the parents not only protect the eggs, but also protect and raise the fry
For each of these behaviours, there are species of fish that will present a challenge to even the advanced aquarist, but there are also species that can be spawned by even the newest novice among us – indeed, often it becomes a problem trying to get them to stop, when every shop in town is already flooded with your fish and you come home to find yet another group. No matter how much or how little experience you have, there is no reason that you cannot experience the pleasure of witnessing your fish breeding, and within each of the categories we will look at both some easy and some challenging species of fish.
Of course, as with all generalities, there are exceptions or enhancements to the four categories. Some fish appreciate that parental care will enhance the chances of their offspring, but can’t be bothered to do it themselves. Like the cuckoo, they deposit their eggs secure in the knowledge that someone else will have all the tribulations of rearing them. The bitterling (Rhodeus spp) hands over the responsibilities to a mollusc – the swan mussel (Anodonta sp) or one of its relatives. Mussels usually close up tight if they are knocked or startled, so first the fish acclimatise the mussel to their activity, bumping against it until it appreciates they are no threat and ignores them. Then the female deposits the eggs inside the mussel, and the male’s sperm is drawn in by the normal inflow of water used by the mussel for breathing and eating. The bitterlings then depart, taking no further interest in their family. Meanwhile, inside the hard protective shell of the mussel, the bitterling eggs hatch safely. The little fry continue to live and grow inside. Eventually, when they are over half an inch long and much better able to look after themselves, the little bitterlings leave their foster parent to join the wider world. This doesn’t sound very fair to the mussel, but it does get its own reward. When the mussel spawns, the larval offspring (glochidia) attach themselves to fish until their larval stage has passed. In the aquarium bitterling are very easy to keep. Either a small shoal or a pair will live happily in an unheated tank, and they are unfussy about feeding. Unfortunately mussels are a different story. They need very clean aquaria, and even then may sometimes die. If the mussel remains open and does not respond to being tapped by closing, it is dead and must be removed quickly. It is a good idea to have a separate mussel tank or small pond, and replace the mussel in the bitterling tank regularly. Of course, you will need to keep an eye on your mussel tank or pond for the appearance of your new bitterlings!
Synodontis multipunctatus is also known as the Cuckoo catfish, because it too offloads its offspring onto someone else – in this case Lake Tanganyika mouth brooding cichlid females. Along with S. petricola and S. eurystomus they spawn at the same time and place as the cichlids, and then when the cichlid mother takes the eggs into her mouth for protection she also takes in the catfish eggs. These are somewhat more malevolent than the bitterlings – just as the cuckoo bird nestling throws out all the eggs that were laid by its foster parents, so the catfish fry hatch earlier and get a good start in life by devouring the yolk from the cichlid eggs. As they grow on this nutritious food, they progress to eating whole eggs and then any cichlid fry that have managed to hatch. This behaviour has been reproduced in aquaria, but if no cichlids are present they have been documented as simply scattering their eggs, which can then be scooped up and hatched in a tumbler. Those aquarists who have reproduced the cuckoo behaviour often keep them with Malawi mouth brooders – there is even a record of the South American Geophagus steindachneri being successfully used, so they are able to recognise cichlids they would not naturally encounter as being suitable.
Where only one of the parents cares for the eggs or young, it is most often the male. Males of many species establish territories or build nests, and often their resulting family may include eggs from more than one female. In some species, the male may carry his eggs with him, rather than remaining in a ‘nest’. Mouth brooding cichlids are well known to aquarists, and in this case it is the female who shoulders the burden of caring for the family. However, in many species, including the mouthbrooding bettas, it is the male who takes charge of the eggs. The seahorses (Hippocampus sp) and pipefishes take their care one step further though; the male has a special brood pouch on his stomach. The female deposits her eggs into the male’s pouch, where he can be reasonably certain that any fertile eggs have indeed been fertilised by him. The eggs, and the new hatchlings, remain inside the pouch until a relatively advanced stage of development. When it is time for the little seahorses or pipefishes to leave home, the male ‘gives birth’, when strong contractions in the pouch and the contortions of the male result in the young fish being ‘fired’ from the pouch in spurts with each contraction. Although usually the male is the prime carer (in 36 of the 77 families in which the sex of the caregiver is known the male alone cares for the fry, and in many others he shares the care) there are many species, including many mouthbrooders, where the female does not escape her responsibilities. In Banjo catfishes the female carries the eggs with her, attached to her stomach by minute threads. It has been suggested that these threads may pass oxygen or nutrients to the developing fry within the eggs – not beyond the bounds of possibility, considering that the goodeid livebearers nourish their developing fry inside their bodies by attachments known as the trophotaeniae.
Although some of these particular weird methods can be observed in the aquarium – seahorses can be bred in captivity by the most committed of marine fish keepers – the majority of the fishes we keep fall into one of the main categories. However, they still manage enough variations to enthral all but the most jaded aquarist, and there are certainly plenty of species who are known to offer a challenge, or even those whose breeding behaviour still remains to be documented. Providing suitable conditions and watching your fish spawn (not to mention raising the fry) provides one of the most interesting and satisfying facets of fishkeeping, and if you haven’t yet heard the flutter of little fins, then now is a good time to start your first spawning project…
Many of our most popular aquarium fish are egg scatterers. In this form of reproduction, the male and female come together at spawning time, liberally scatter the aquarium with usually vast numbers of eggs, and then forget all about them. Often the parents, hungry after their exertions, will go round the aquarium and eat the eggs they have just produced. Egg scatterers are, in general, ideal for life in a community tank. Because they have no interest in their offspring, they have no reason to bother holding on to a territory, and are therefore usually peaceful. If any fry are to survive, given the disinterest of their parents, there have to be a lot of them – the law of averages is the only thing they have on their side, and the more there are the higher the odds that a few will survive. In the community aquarium, however, the odds are already stacked against them. If they hatch in a river or lake, there is usually a lot of space, including shallows or heavily overgrown areas where the big fish cannot reach them. In an aquarium they are not only very limited in the number of places they can hide, but there is a large population of hungry fish continually hunting in the same area. Although they may often spawn in the community aquarium, the aquarist must set up a nursery tank if any are to grow to maturity. Often, in practice, this nursery tank will be set up in a state of panic, when the aquarist comes home to find a tank full of eggs and his fish busily engaged in hunting them down. ‘Tank’ is often an overstatement – in an emergency a bucket with a heater and a sponge air-powered filter is perfectly adequate. A bottle of biological filter starter should be a part of every aquarists emergency kit; with a good dose of this every day for a few days a new tank (or bucket) can be set up safely and quickly. A rearing tank is usually best without any substrate; this avoids mislaying bottom-dwelling fry, and also allows the aquarist to siphon out the dirt more easily. Air powered sponge filters will not suck in and ‘filter out’ tiny fry, and moreover also grow colonies of microorganisms on their surface which can provide a food source for fry. Alternatively, the more organised aquarist may plan for his new family, by setting up a spawning tank and stocking it with a nice fat female and her mate, who can be removed once the happy event has taken place.
There are many egg scatterers who are ideal for a starter project. In an unheated tank goldfish will often take the initiative themselves. You will know when the happy event is imminent by the behaviour and appearance of the fish. Females become very fat, often lopsidedly – looking at the fish from above one side will be fatter than the other. Males begin to show raised white spots on the gill covers and upper lip – these are known as tubercles, and are not the first sign of some dreadful disease, but perfectly natural. When they are nearly ready to spawn the males will start chasing the females around the tank. At this time they need to be provided with lots of plants (copious elodea is ideal).
You can trigger the spawning by a water change or by lowering the water level. Usually early next morning you will hear the frantic splashing as the males drive the females into the plants, and the plant fronds will soon appear to be decorated with tiny pearls. Although goldfish are enthusiastic egg eaters, they are also very prolific, and provided there was enough dense planting there will almost certainly be plenty of eggs for you to remove (still attached to the plants) and rear. With goldfish, as with many egg scatterers, you must be careful not to bite off more than you can chew – if you carefully rescue every egg, you are going to need a small reservoir to rear the fry. About twenty eggs is a good number to remove, taking care not to choose those that are white and opaque (these are the infertile ones), and if you are one of those who has set up the emergency bucket, now is a good time to start getting a large tank ready to hold them.
When the eggs first hatch, the fry are visible clinging to the glass and look like tiny glass splinters. After two or three days they will become free swimming, and at this time need to be fed. Proprietary fry food from the aquarium shop is taken enthusiastically, and they grow rapidly. Do not be disappointed that they are all brown – all little goldfish are, and they will start to get their adult colours when they a between an inch and two inches long.
Corydoras catfish are not strictly egg scatterers, as the female will carefully place each egg rather than just scattering them around, but the same principles hold true, as she takes no further interest in them. Bronze Corydoras (Corydoras aeneus) are the first fish to spawn for many aquarists, and produce large numbers of eggs. They will eat packaged fry food, but particularly enjoy baby brine shrimp. These have the added advantage of reassuring the aquarist that they are eating – all the little fish will have orange, rounded, brine-shrimp-full tummies. The two Corydoras mentioned will spawn happily in most community tanks, without any special preparations. There are, however, lots of different species, and some are challenging spawning projects, requiring soft water and live food to inspire them.
One of our most popular aquarium fish is the neon tetra (Paracheirodon innesi), and it’s cousin the cardinal tetra (Paracheirodon axelrodi). Although these make their appearance in just about every small community tank, spawning them is somewhat more tricky. In community tanks they are adaptable to a range of water chemistries, but for spawning require special effort to provide them with conditions similar to their Amazonian home. Rainwater in which peat moss has been soaked provides the soft acidic conditions similar to their blackwater homes. The pH needs to be low, at about 6.2 or lower (in their natural habitat the pH can be as low as 5).
To condition the fish, separate the males and females, and feed them as much live food as they can cram into their hungry little mouths. They can be spawned in groups or trios, but a single pair of a nice fat female and a healthy male should produce plenty of eggs. Place them together in the spawning tank, which should have fine leaved plants or spawning mops. A mesh at the bottom of the tank, through which the fish cannot swim to reach the eggs, will stop them eating most of them. When the fish have finished spawning, this will be evident by the reduced waistline of the female. The parents can then be removed, and the tank covered to keep it dark. The eggs will die if kept in the light. This is also a good time to start an infusoria culture – neons aren’t very big as adults, and the fry will need very small foods. You can feed them on packaged fry food for egg-layers, but suitably sized live additions will help their growth. Throughout their rearing, it is essential to keep the aquarium and water clean. Neon tetras can produce around 500 eggs, so unless you have a very big tank (or tanks) you will need to thin them out periodically. Overstocking leads to bad water quality, which will rapidly result in severe understocking!
We tend to think of fish as being difficult to spawn or easy to spawn. In reality all fish are easy to spawn – after all, they do it perfectly well in their natural habitat. What is difficult is working out the precise set of conditions which the more fussy fishes require. Once the required conditions are known, then it is simply a matter of giving them those conditions. In general, you can judge whether a fish will be fussy or not from its wild distribution. If they are widely distributed over a large geographical area, then they are probably quite tolerant. If they are found only in very specific conditions, then there is probably a reason for that, and you need to expect to have to reproduce their natural conditions quite closely.
For many fish, simply spawning with gay abandon and then swimming off leaving the eggs to the care of the fates is not enough. One of the parents, usually the male, prepares the spawning site, either simply by selecting it or in some cases building a nest, and then charms the female into his selected site to spawn. All these males are quite protective of their little spawning zone, especially against other males of the same species. After all, if you are going to invest all that time and effort preparing and guarding first a nest site and then the eggs that are laid there, you certainly don’t want any suspicion that some fishy Casanova might have sneaked in and fertilised the eggs! This makes these fishes slightly less suitable for the community tank, and certainly not in groups of the same species.
Egg guarders are usually best kept as a pair, or a male and two females. While they are likely to take severe objection to any other male of the same species, they are rarely very aggressive towards fishes of other species except in the small nest zone. Most large communities have enough room to allow a few fishes that are so inclined to set up and guard their bolthole; after all, we are not talking a great deal of space, perhaps one corner for a bubblenest or a small cave. Although this behaves limits the community aquarist to keeping only two or three of each of such species, they do have a great advantage for anyone who wants to rear the fry. If you do not happen to be present for the actual spawning, the fish will protect and care for his eggs until they hatch. This gives you plenty of time to set up a nursery tank for the little fish.
Bristlenose catfish, especially the common Ancistrus temmincki, are ideal fish in this group for a beginner. The males and females are easily told apart (the males are the ones with bristles) and provided they are fed a good diet will almost certainly spawn. There has been many a fishkeeper alarmed or surprised by the sudden appearance of a few black tadpole-like creatures in his tank – survivors from an unnoticed bristlenose spawn. The male guards his family (which may include eggs from more than one female) carefully and diligently. He remains with the eggs for the three or four days until they hatch, never leaving them even to eat. He continually fans the eggs to ensure a constant supply of new, oxygenated water, and continually works over the cluster (which looks a bit like an orange raspberry) to remove any damaged or fungused eggs that could spoil the whole brood. With this care, you may wonder as to why the surprised aquarists had only a few – bristlenoses can easily lay over a hundred eggs. This is because although the eggs are cared for, the father rapidly loses interest in the fry. He will not harm them, but as one by one the little yolk balls with tails escape the nest site, he ends up with an empty cave. Of course, the other fish in the tank enjoy nothing more than a tasty egg yolk, with a bonus little fish attached to make them even tastier. Ideally the egg cluster should be removed (moving the whole piece of décor or bogwood to which they are attached into a plastic bag full of water is a good way of transferring them, and quite often the male will remain in place and go with them) to a waiting nursery tank, where often you can get a 100% survival rate. Fortunately, most shops are delighted to receive little bristlenoses, as these fish always sell well.
The dwarf gourami (Colisa lalia) is another devoted father. He takes in air at the surface and blows it through his gills to produce mucous-coated bubbles, which stack up at the surface in the chosen area. Sometimes he will augment the bubbles with carefully chosen bits of plant or debris, until he has a structure several inches square and up to an inch high. Once he has a bubble nest, he has two aims in life – to deter any of the other tank inhabitants from coming near it, and to convince a female gourami to lay her eggs in his nest. It is best to keep the fish in a fairly large tank with lots of hiding places, as if a female is not ready to spawn the male becomes frustrated and may harm or even kill her. Plenty of live food usually ensures that the female is full of eggs, and when she is ready she moves underneath the bubbles with the male. The male curls his body around hers, and the two fish slowly sink together through the water, emitting eggs and sperm. When they reach the bottom they remove unmoving for a few seconds, and then the male chases the female away while he carefully gathers up all the eggs and spits them into his bubble nest. This mating may be repeated many times until the female has no more eggs.
The male then patrols under the nest, performing repairs as necessary with new bubbles, and keeping away all the other fish who might eat them. Held as they are in a mass of bubbles, the eggs have ample oxygen to hatch. After two or three days, inspection will show lots of tiny black strings hanging down from the nest. At this time, or even earlier, the whole nest can be scooped out in a bowl and transferred to a nursery tank. This is necessary, because once the male sees the little tails wriggling, he forgets all his careful parental efforts and starts to see that his offspring could be quite tasty… The little gouramies do need some specialist care. As airbreathers, they will need to breathe atmospheric air very early. This means that the water should be shallow, and the air above needs to be kept warm and moist, so as not to be too much of a shock for the little fish. Clingfilm is ideal for covering the tank, with an airline pushed through it powering a sponge filter. The fry are extremely small, so you will need lots of tiny food like infusoria – the staple baby brine shrimp are far too big for a first food.
Dragon gobies (Rhinogobius wui) are entertaining egg guarders for a small aquarium. The male establishes himself by digging a hole under a flat stone, and can then be seen showing off around the tank, throwing his head back to expose his red throat, and becoming darker. Then, one day, he is nowhere to be seen…. This is not cause for alarm. Having persuaded a female to produce some eggs for him, he has retreated into his hole and closed the entrance behind him. There in his little sealed cave, he cares for the eggs until the are ready to hatch. Unfortunately, he is not to be trusted with the fry, and removal of the stone to a nursery aquarium after three days gives the eggs little chance to fungus without the male, and ensures that they hatch safely in the nursery tank. The little gobies are easy to raise – keep them stuffed with brine shrimp nauplii and they eat and grow rapaciously. The goby family has many representatives, many of which represent far more of a challenge to the would-be breeder.
The Spraying characin or Splashing tetra, Copella arnoldi, has a unique problem when it comes to guarding its eggs. They are in no danger from other fishes, but are likely to dry out without constant attention! This is because this little characin deposits its eggs on the undersides of leaves overhanging the water. The male and female position themselves carefully and then leap as much as 10cm into the air, turning upside down and adhering briefly to the underside of the leaf, where they deposit between 5 and 8 eggs. This process is repeated until the spawning is completed, with between 150 and 200 eggs produced. The female then goes her own way, but the male remains in attendance, splashing the eggs with water every minute. He even manages to correct the angle for the refraction of the water. As the eggs hatch, the fry drop down into the water. In the aquarium, of course, there aren’t usually that many overhanging trees, but the undeterred characins will spawn on the underside of the aquarium lid or cover glass. These require soft to neutral water, between 6 and 7.5 pH, and soft water with a dH between 5 and 12.
Egg guarders usually cause little trouble in the aquarium, and are the perfect group for the community keeper who would like to try rearing some spawn. As the male has to attract the female to the place of his choosing, their spawning behaviour is usually noticeable and interesting, as well as the subsequent care for the spawn. Most, however, will eat the fry once they have hatched, and lose interest in protecting them, so you still need to provide a safe haven for the fry if you hope to rear any to adulthood.
Some of the livebearing fishes are among those recommended to every beginner – the guppy (Poecilia reticulata), the platy (Xiphophorus sp), and the swordtail (Xiphophorus sp). The molly is another livebearer often recommended for the new aquarist, but is not as hardy as the previous three – it does need hard water, and prefers brackish, otherwise it is prone to a variety of ailments. These fishes are available in an incredible array of colours and forms – there is a guppy to suit every taste, and probably a platy or swordtail as well. In addition to their beauty, they are also easy to breed. All these easy to keep fishes are members of the family Poecilidae, and give birth to little tiny fish rather than laying eggs. They also practise internal fertilisation, and the males do indeed practise every chance they get. For this reason it is better to keeper a higher number or females than males, to spread the attention and prevent any one individual being harassed non-stop. Fortunately it is easy to tell the sexes apart, as the male’s anal fin has evolved into a long thin rod, known as a gonopodium. This is used to inseminate the females. Female fish have anal fins that are an ordinary triangular shape. Another common feature of the poecilidae, and indeed most live bearers, is that the males are usually smaller and better looking than the females.
Male swordtails are the only sex to bear the sword (an extension of the caudal fin), while male guppies are brighter coloured than females. For those who like all their fish to pull their weight in the beauty stakes, the endearingly rotund little platies are brightly coloured regardless of sex. Once you have at least a male and a female of these fish, the female will get rounder and rounder, and then one day she will suddenly be thin again, and the plants will be full of little fish hiding. If you keep them in a community aquarium, at least a few of the offspring will probably survive the depredations of their tankmates (often including their parents) provided that there are some plants to act as cover.
Little guppies head for the top as soon as they are born, so need floating or tall plants, while little platies head for the bottom, and will need profuse planting there. If you wish to raise a good number of the babies, however, you will need a breeding tank. Ideally, the female should be placed in the breeding tank a week or so before the birth is due – you will soon learn to tell by her waistline. This is because moving her once she is at the point of giving birth will be very stressful for her, while waiting for her to give birth before trying to catch and transfer the youngsters will result in many stressful hours (for both you and the fish) with the net. There are breeding traps for sale in most shops, which consist of a floating plastic box or net in which the female can be placed, the youngsters being protected inside from the community of eager mouths. Unfortunately the female fishes don’t like these – they offer a very small amount of swimming space in which the fish still feels exposed, and more delicate species may abort. The hardy varieties will probably survive the experience, but it won’t do them much good in the long run.
Little poecilids are very tiny – the mother simply holds the eggs inside her while they hatch. There are, however, quite a lot of them – mature guppies can produce a brood every four to six weeks, and one birth of 193 fry was recorded. Although this is exceptional, the numbers can still get quite high, especially as any surviving offspring will reach breeding age in around three months. You might think that removing the males would put a stop to the breeding while you get the population under control, but you would be wrong – the poecilidae store sperm, so that one mating can last for several pregnancies. This is an annoyance to anyone who wants to create a new colour strain, or breed specific fish with other specific fish – once a female has mated, there is no guaranteeing the father of her fry thereafter. For this reason, if you want to arrange specific matings, the female must be separated from all males before she reaches breeding age. Of course, these popular fishes are not the only livebearers around.
The large Poecilidae family offers many other ‘wild form’ species suitable for a beginner, including a variety of wild platies and swordtail and the wild guppy. There are also such fish as the hump-backed Limia, Limia nigrofasciata, the Merry Widow, Phallichthys amates, and Holbrook’s mosquitofish, Gambusia affinis holbrooki, all of which are relatively easy to keep and breed. For the experienced aficionado who wants a challenge, the family also offers the aggressive and predatory 8” Piketop minnow, Belonesox belizanus, the shy and tiny dwarf swordtail, Xiphophorus pygmaeus, and many others. The advanced aquarist who wishes to try some of the wild forms or a specific strain of a cultivated species should be aware that closely related fishes, e.g. different platy species, platies with swordtails etc, can and will hybridise.
Although aquarists refer to ‘the livebearers’ as though they were one big family, there are many completely unrelated fishes who have evolved ways of livebearing. The ancient and huge Coelacanth is a livebearer, as is the whale shark. These are unsuitable not only for we aquarists, but even for public aquaria! Fortunately there are plenty of livebearers which can be kept. The goodeids are attractive, and relatively easy to keep. The Butterfly livebearer, Ameca splendens, is a beautiful and easy to keep fish. Its only drawback is that it is highly aggressive. However, at up to three and a half inches long, it is well worth setting up an aquarium for a pair, and as a bonus they do not generally eat the fry. Ameca belongs to the Goodeidae family, and although the male anal fin is modified in the goodeids, it is not like the long thin poecilid gonopodium. Rather, the male simply has a notch in the front edge of the fin. This is not the only biological difference – a goodeid pregnancy is much more like a mammalian pregnancy in that the female nourishes the young as they develop inside her. This is done by the growing structures called trophotaeniae, through which they can gain nourishment from the mother. This results in smaller numbers of large fry being born, on whom the vestiges of their trophotaeniae can be seen like little umbilical cords. These quickly drop off once the fry are born. For those who don’t fancy the aggressive Amecas, there is the delightful little Crescent Zoe (Zoogoneticus sp) from western Mexico. These are far more peaceful, and have a beautiful yellow crescent in the tail fin. These only grow to about two inches, and can be kept in a community – of course in a community the fry will be endangered by the other inhabitants, so a breeding tank will be necessary. Unlike the poecilids, the goodeids do not store sperm, so a male is necessary for each pregnancy.
One of the most curious fish available to aquarists is the four-eyed fish, Anableps anableps. This does best in a species aquarium with brackish water, and is definitely one for the specialist. The ‘four-eyed’ name comes from the fact that each of the fish’s eyes is split into two parts. As the fish lies at the water surface, the upper half of the eye sticks up above the surface and watches, while the lower half of the eye views the scene underwater. These large fishes (growing to a foot long) produce only a small number of fry, and that not very often. Up to thirteen fry in a brood have been recorded, but usually there are around six, and the broods are spaced six months apart. Each of the fry can be up to 4cm long. The male four-eyed fish has its anal fin modified to form a gonopodium, but the rays are twisted round one another and the whole gonopodium points either to the right or to the left. This is the only point of similarity for the non-taxonomist between the four-eyed fish and its close relation, the one-sided livebearer (Jenynsia lineata). This is a relatively small (females can be up to four and a half inches, while the tiny male only achieves one and a half) fish, which has entirely normal eyes and swims normally. It does, however, have a similarly twisted gonopodium, and it is reputed that a right-sided male can only mate with a left sided female, and vice versa. These also produce large fry, every five to seven weeks.
These fish mentioned are only a few of the fascinating livebearers available to aquarists. Some, however, are rare in aquatic shops and best purchased from specialist breeders. No matter your level of expertise or the type of aquarium you keep, there will be a livebearer suited to you. Witnessing the birth of the tiny fish is an experience every aquarist should sample at least once.
These fishes are among the most rewarding to watch as they pursue their normal spawning behaviour in the aquarium. However, they are also the least suitable for keeping in a normal community. Not only do the parents need to set aside a small piece of tank to call their own as a territory, but when the fry hatch they are, rather like human children, prone to sneaking away from the group as soon as their parents backs are turned to investigate anything interesting that catches their eye. Their parents know that any fish in the vicinity is likely to get a chance sooner or later, so they are very intolerant of any other fishes. This behaviour is the hallmark of the large family known as the Cichlids. Most aquarists fall into one of two groups fairly early in their fishkeeping career – those who swear off cichlids altogether (often after an encounter resulting in a high death count in a peaceful aquarium) and those who are entranced by them to the extent that their interest is entirely taken up by this group. However, while there isn’t a cichlid to suit everyone, there is certainly one to suit most people. There are relatively peaceful fishes, of which a pair can settle into most large communities; there are small species such as the Apistogrammas and the cute shell-dwellers, who are so small that finding room for a species tank won’t be a problem, and there are large and aggressive fish who often end up as ‘pet fish’. There are easy to keep ones, and shy pernickety ones.
One of the most popular cichlids is the Krib, Pelvicachromis pulcher. Relatively small, at up to four inches, they easily live up to their latin name of pulcher, which means beautiful. Although they guard both their eggs and the fry carefully and diligently, they are not so aggressive that they cannot be kept in a community. In a three foot (or larger) aquarium there is enough room for a single pair of kribs to set up home together and for the other inhabitants to keep out of the way. You can assist in this by providing plenty of plants and décor to break the line of sight, and a cave or upturned flower pot for the hoped-for krib family. Males are larger than the females, and frequently have spots on their tails. The female is plumper, and when she is ready to start a family her belly becomes purplish red. If you obtain several small kribs, you can keep them until two pair off, and send the rest back to the shop or to other aquarist friends. You will easily know when love is in the air for a pair – this is when they stop being so mild-mannered and become very possessive about their cave. The female often displays for the male, standing still in the water and ‘shivering’ her whole body. Both sexes become obviously more colourful. If all is successful, eggs will be laid in the cave, and both fish guard the eggs. Careful examination of the tank may reveal a little family of tiny fry, almost invisible against the substrate. Both parents take excellent care of them, shepherding them back to their cave at night and continuously rounding up stragglers. As the fry go, the parental care becomes less diligent, until one day there is a new family and the old fry are now persona non grata. They should be removed, as they will soon be big enough to set up their own households.
In most cichlid families, the last offspring are ousted when a new brood arrive. However, in a number of African cichlid species, the most notable being the Tanganyikan Neolamprologus brichardi, fry will stick around for about a year, through two or three subsequent broods. Rather than regarding the newcomers as competition, the older fry help the parents look after the new family. Performing duties such as egg cleaning, fry guarding, and territory defence, these older fry grow more slowly than those who leave home, but continue to reap the benefits of safety afforded by the territorial home.
An ideal fish for a small species aquarium is the shell dweller, Lamprologus ocellatus. These pretty and endearing little fish will appreciate a few large apple snail shells (or edible snail shells available from your local delicatessen for serving snails in!). The little two inch fish are best kept as a male with several females (unlike the kribs, the male Lamprologus is a womanizer!). Each female will stake a claim to a shell, which eventually she lays her eggs in. The male waits outside, and as the female emerges from the snail shell, produces his sperm. The water drawn into the shell as the female leaves carries the sperm inside, which fertilises the eggs. Being promiscuous, the male take less interest in the eggs and fry than many cichlids, which are primarily guarded and cared for by the female.
One can hardly consider cichlids without mentioning the Discus (Symphysodon sp), regarded by its fans as the ultimate aquarium fish. These softwater Amazonian fishes come in a range of beautiful colours, and are careful and attentive parents. After obtaining a group of young fish, it should not be too long before a pair forms, and the unpaired ‘spares’ can be rehomed. The adults lay several hundred eggs on stones, plants, or a vertical surface such as the tank glass, and guard and pick over the eggs constantly to ensure that no fungus can develop. These fish must be spawned in softwater, as the eggs are unable to withstand harder waters. According to many discus keepers, these fish are about as hardy and easy to keep as a snowflake – they are apparently best kept alone in pristine bare tanks. Many people do keep discus in planted aquaria with a few companions – those that share their water requirements should not cause any problems, and Corydoras are often a good choice. Once the fry are hatched, discus are unusual in that they produce a skin mucous on which the young fry feed for their first few days.
Whether you become a confirmed cichlid fan or a discus specialist, or just want to experience the fun of seeing a little family of fish growing up in your tank without too much trouble, one of the huge number of cichlid species will suit your purpose. Even if it does mean that you need to set up a special tank, you will find the pleasure you get, first from the courting of your fish and then the emergence of the first family, well worth the effort.