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Nothing in the hobby is as rewarding as rearing a batch of baby fish. Whether it's simply a few newborn guppies found swimming around a community tank or an organised attempt to breed a tricky tetra or killifish, fish breeding is by far the best test of an aquarist's skills. Fish breeding is also a great way to rekindle enthusiasm for the hobby and to draw in other family members. Children in particular don't always grasp the subtlety of cichlid behaviour, but they will certainly appreciate the sight of a pair of kribs protecting their batch of newly hatched fry. Watching baby animals growing is always a delight, but it is also proof that your fishkeeping skills are mature.
In this article we'll be looking at three species that make interesting but easily achievable fish-breeding challenges, one from each class of fish: egg-layers, mouthbrooders, and livebearers. One of the things that people often find off-putting is the whole process of raising live foods for baby fish, typically newly hatched brine shrimp (Artemia nauplii) and microworms (the nematode worm Panagrellus redivivus). But not al newly hatched or newborn fish need such fiddly foods, and some can be reared perfectly well on liquid and flake foods designed for use with baby fish. Among the liquid foods, Liquifry has been popular among aquarists for decades, and the finely ground flake foods sold by companies such as Tetra and ZM Foods are just as easily obtained from most aquarium shops.
Before looking at the selected fishes in depth, there are some concepts that need to be reviewed. The first is the importance of water chemistry. While many fishes will tolerate quite wide ranges of pH and hardness values, when it comes to breeding they are often a good deal more particular. Sometimes they may spawn in the wrong water conditions, but the eggs will not hatch, or if they do, you end up with a batch of fry almost all of which are of just one sex. Other species simply won't spawn until the right water conditions are attained. Broadly speaking, you will need to aim for water conditions similar to those in the natural habitat of the fish in question. So for kribs, neutral, moderately hard water like that in the Niger Delta is desirable, while many Corydoras prefer soft, acidic water like that in the Amazon River basin. Swordtails come from rivers flowing over limestone, and expect hard, alkaline water, and mollies will want something similar, but will a little salt added as well to create brackish water conditions mimicking their coastal stream habitat.
Selecting and conditioning your breeding stock is the next important issue to consider. When breeding your fish, you do need to give a thought to what you will do with the resulting juveniles. Most aquarium shops will take excess fish, often paying you in credit that you can spend in their store. But shops only want decent fish that they can sell. They don't want fish that are all of one sex and they certainly don't want fish that are deformed or otherwise unattractive. If you're breeding livebearers, stick to keeping a single strain, so that the fish you take in to the store are all of a type. Once you've decided what it is you want to breed, you need to condition the parents. This involves nothing more that giving them the best possible diet. Live foods are often recommended for this, though frozen foods seem to work well in most cases. The female fish in particular need lots of extra food so that they can produce a large clutch of eggs, each of which needs to be given its own store of food, the yolk sac. Mouthbrooding fish often go for days or weeks without eating, so obviously need to have some fat reserves to draw on as well.
This brings are neatly to spawning triggers, events that cause fish to breed. In the wild, fishes schedule their breeding to coincide with optimal conditions. A common example in tropical fish is to begin breeding at the time of the annual floods that expand the aquatic habitat and greatly increase the amount of food available for the baby fish. A side effect of the conditioning process just mentioned is that the abundance of high quality food suggests to the fish that the floods have come. Changes in water temperature can be useful, too. Some species spawn when cooler water is added (to mimic rainfall) while others will only respond when the temperature goes up (because they breed during the summer). Corydoras are examples of the former, and angelfish of the latter. Many species synchronise their spawning, meaning that all the individuals in the social group lay their eggs at the same time (salmon, with their annual runs up rivers, are the classic examples of this). Among aquarium species, a very common spawning trigger of this type is early morning sunshine, with a variety of species using this as the signal to begin breeding. Included among such species are danios, Corydoras, and glassfish.
The majority of tropical fish are egg-layers, either scattering their eggs among plants or on the substrate, or else carefully guard the eggs within a nest. Tetras, barbs, and danios are examples of egg-scatterers, while cichlids, gouramis, and most suckermouth catfish are nest builders. In practical terms, these are the most difficult fish to breed for two reasons. Firstly, fish eggs are small as are the resulting fry, which makes them difficult to feed. Most egg-laying species require tiny live foods of one type or another, ranging from infusorians (single-celled pond animals) through to Artemia nauplii and microworms, though there are exceptions. The second issue is that under aquarium conditions fish eggs are peculiarly vulnerable to fungal infection, revealed by the development of fine white strands on the outside of the egg. This fungus usually starts on infertile eggs, but can spread to healthy ones, quickly killing them. The addition of anti-fungal medication will help, as does increasing the aeration in the aquarium to create a steady flow of clean water across the eggs. Many of the nest-building species will try to keep the eggs free of fungus, removing any infected ones, but with the egg-scattering species, this chore defaults to the aquarist.
There are a number of egg-laying species that can be considered ideal species for beginners -- kribensis, danios, and ricefish among them -- but the peppered catfish, Corydoras paleatus, is one that balances a variety of interesting issues worth considering. At a basic level, this is an easy fish to breed. It will breed most readily in soft to moderately hard, acidic to neutral water. As a subtropical species, it can be easily conditioned in a garden pond during the summer months, where it will have access to a variety of suitable live foods. The eggs are fairly large and the resulting fry big enough to accept liquid and powdered fry foods. But there are some complicating factors. Corydoras don't breed in pairs but in groups, typically with two or three males following a single female about. Eggs are not shed randomly but carefully fixed in small clutches to clean, flat areas such as smooth stones, large leaves, and very frequently the sides of the aquarium. Females release a few eggs into a 'cup' formed by their pelvic fins, and one of the males then fertilises them. The female carries the eggs to a suitable spot, cleans the area with her whiskers, and then attaches the sticky eggs in place. The process is then repeated dozens of times across the aquarium. Corydoras eggs are whitish in colour and semi-transparent. Although soft and sticky at first, a few hours after being laid they become tough enough to be moved if this is required. Corydoras paleatus generally ignore their eggs, at least to begin with, but it is wise to take the parents out of the breeding tank after they have finished spawning. The eggs hatch within five days, and the fry a free swimming the following day.
Mouthbrooders are fish that protect their eggs (and often the newly hatched fry) inside their mouths. Mouthbrooding has evolved among a variety of fishes including arowanas, catfish, cardinalfish, bettas, and gouramis, but it is perhaps best known from examples among the cichlid family. Most of the mouthbrooding cichlids are rather large, but the species in the genus Pseudocrenilabrus are small mouthbrooders and consequently make ideal subjects for the aquarist interested in seeing this fascinating behaviour for the first time. Several species are available that are all very similar in terms of temperament and care, but Pseudocrenilabrus nicholsi is the standout species thanks to its vivid red and blue colouration. Male fish are simply gorgeous, with colours that rival any coral reef fish. Females are smaller and rather drab by comparison. The only reason these fish aren't more widely sold is that the males are remarkably aggressive given their size, and are best housed with larger fish such as mbuna, plecs, and robust barbs and characins.
They are not difficult fish to keep or breed; neutral to slightly alkaline, moderately hard water suits them best, and they can be easily conditioned on good quality flake and frozen bloodworms. The female broods batches of a few dozen eggs for about ten days, after which point the fry hatch. The fry will immediately eat finely ground flake, algae, and general aquarium detritus. For the next week or two the mother will bring them back into her mouth if alarmed, but it is actually best for the aquarist to remove the fry and let the female recover from her enforced starvation. For obvious reasons, while mouthbrooding the female cannot feed. Separating the mother from her fry is tricky, but one good trick is to place her head-downwards in a turkey baste filled with aquarium water; a gently squeeze will force water into her gills and push the fry out of the spout and into an awaiting breed net or trap. She can then be fattened up away from the male. It isn't a good idea to put her back with the male for at least a month after brooding.
Breeding livebearers is relatively simple because the resulting fry are large enough to take flake and liquid foods straightaway, and many species will also feed on green matter such as algae. On the other hand, pregnant livebearers can be shocked into miscarrying their broods by things like sudden changes in water chemistry, rough handling by the aquarist, or stress caused by any aggressive fish in the tank. Another problem is the quality of the fish used for breeding: commercially produced fancy livebearers are sometimes of indifferent quality, with physical defects like bent spines and imperfect colouration being common. The offspring from such parents are not especially desirable, and the aquarist will find it difficult to find homes for deformed fish. So while livebearers certainly rank among the best species for newcomers to the fish breeding game, they are not without their problems.
An unusual livebearer that is typical of the group in general is the butterfly goodeid, Ameca splendens. Its natural range is the Rio Ameca in Mexico, where the water is hard and alkaline and in fact not very different to the water enjoyed by most aquarists in Southern England. Care is essentially similar to that of the more common livebearers, though it is rather more aggressive and is best kept on its own. As with most other livebearers, these fish are primarily herbivorous and need to be conditioned with both an algae-rich flake food as well as small live foods such as mosquito larvae and daphnia. Livebearers generally don't have spawning or pairing behaviour as such; instead, the males will simply try to fertilise any females in the aquarium with them. After a few days you can safely assume the female is fertilised and remove her to a separate birthing tank. With many livebearers it isn't a good idea to move the female when she is within a few days of giving birth, as the stress often leads to miscarriages. Instead, move her early on in her pregnancy. Not only will you avoid losing the young, but she will also do better away from the attentions of the males. The brood will be delivered after 6-8 weeks, and the fry can be reared on finely ground flake and algae.
Box out: The pros and cons of breeding traps
Info box: Additional species for novice fish-breeders
Common name: Zebra danio
Water chemistry: Adaptable, but soft and slightly acidic to neutral is best
Conditioning foods: Small live and frozen foods such as bloodworms and daphnia
Spawning trigger: Early morning sunshine
Spawning method: Eggs are scattered on the substrate, which should consist of small pebbles or marbles to prevent the parents eating them
Brood care: None
Brood size: Broods of several hundred not uncommon
Hatching time: About one day
Free swimming: Anything up to five days after hatching
First food: Ideally small pond foods, microworms, and newly hatched brine shrimps, but liquid fry food followed by finely powdered flake usually works well
Common name: Kribensis, krib
Water chemistry: Neutral pH essential for a balance of sexes in the brood
Conditioning foods: Bloodworms, brine shrimps, and daphnia
Spawning trigger: None; will breed freely once settled
Spawning method: Eggs are laid on the roof of a small cave
Brood care: Initially the female guards the eggs and the male protects the cave; once the fry are swimming, both parents protect the brood
Brood size: Around a hundred
Hatching time: Three to four days
Free swimming: Two or three days after hatching
First food: Algae and general aquarium detritus seems to work for broods born in community tanks, but liquid and finely powdered flake foods make useful staples for baby kribs
Common name: Guppy
Water chemistry: Hard, alkaline water preferred
Conditioning foods: Vegetarian flake food, algae, and small live foods such as daphnia and mosquito larvae
Spawning trigger: None (just try stopping them!)
Spawning method: Livebearer
Gestation period: Three to four weeks
Brood size: Aquarium strains typically produce around 20-30 offspring
First food: Finely powdered flake, Liquifry, and algae
Common name: Celebes halfbeak
Water chemistry: Prefers fairly soft, slightly acidic to neutral water
Conditioning foods: Frozen bloodworms, live daphnia, and brine shrimp
Spawning trigger: Unknown, but getting the right water chemistry helps
Spawning method: Livebearer
Gestation period: Up to four weeks
Brood size: Normally around ten
First food: Finely powdered flake, Liquifry, and algae
My Aquarium 12/15/11