The tank used for spawning doesn't need to be anything special. Just an ordinary tank of a suitable size will do, but you do need a separate tank. In almost every case you won't be able to get the fish to spawn and raise a brood of fry in a community tank because in most cases the eggs will be eaten before they even hatch.
The tank itself should be kept very simple, there is no need of decor except for a surface to spawn on if required such as a spawning mop, slate or artificial cave all of which depends upon the species of fish which you intend to spawn.
Bare tanks are easiest to maintain but a thin layer of sand will give a much less sterile and will instead create a more natural appearance for the fish and won't interfere to much with cleaning to much.
Don't use any type of power filter thinking that you can make it safe by using some material cut from old tights or stockings to make a fine sieve over the intake area. Although often put forward as a solution this doesn't work in practice. The fry simply get sucked onto the mesh and can't escape due to the power of the filter and as a result they are quickly killed. You could use a variable flow powerhead with a sponge filter.
Use a good quality heater which keeps the temp very constant and avoid using one which allows the temp to vary by several degrees between coming on and off. It is important to keep the tank at the optimal temp for the species of fish you are breeding by doing so you will ensure that the eventual fry will grow at the best rate and make better adults as a result. Anything which slows the fry's progress in the early days will rarely be made up later.
Lighting isn't normally necessary in the spawning tank and it is sometimes the case where it most definitely shouldn't be used. Some fish eggs and fry are light sensitive and bright light will make the spawning fail by killing the eggs. Characins in particular have eggs which are so light sensitive that the tank should be blacked out on several sides prior to spawning taking place.
Some of the medium and larger Cichlids can be very aggressive towards their partners especially at breeding time, and when kept within the confines of an aquarium where escape isn't possible this can lead to injury or even the death of one of the fish. If the fish are of unequal size as is often the case with Cichlids then a mesh tank divider can be used where a small hole has been cut into it which is just big enough for the smaller of the pair to get through but not the larger one. This enables the two to be kept together and allows them to spawn but in relative safety.
A tank divider can be used to separate the sexes while conditioning takes place and it does seem to encourage spawning to take place when the divider is removed and the pair or group are finally allowed to meet after being fully conditioned.
These devices are aimed at the hobbyist who one day discovers a few livebearer fry in their community tank. Deliberately placing a heavily gravid female in an open space directly under a light in the middle of a community tank is wrong on every level and will cause a great deal of stress to the fish and might even cause the premature birth of the fry. If you must use one of these nets in an emergency then place some plants in it too so that the fish has somewhere to hide and some shade.
Small fry won't grow very quickly if kept in one and they won't go on to make good adults in most cases since they'll remain stunted. A separate tank is by far the best option.
I'm not going in depth about pH, GH and KH here because those things are covered elsewhere on this site.
Using the right water for the species of fish concerned can and will make a difference to the outcome. Sometimes the water chemistry will even play a part in triggering spawning.
Soft water species will spawn in hard water but they eggs may fail as a result. This is because calcium in the water makes the eggs outer membrane tougher or it will block up tiny pores on the eggs surface and these two things make it more difficult for the egg to become fertile. Even if the egg does get fertilised it may still fail to hatch.
Other species may not spawn until the pH is low enough.
Do some research on the species that you intend to breed and provide them with the ideal conditions in order to give yourself the best chance of success.
When researching a particular species of fish to breed you may come across the term "aged water" what this means is simply tap or rain water which has been allowed to stand for several days while being aerated there is no need to use any dechlorinator because the chlorine will disappear to atmosphere quite quickly although if your supply has chloramine added instead of chlorine you will still need to use one of the dechlorinators made specifically for it because unlike chlorine, chloramine is quite stable and it will remain in solution.
Once the water has stood for four to seven days it is ready for use. That is all there is to it.
Tannins are naturally occurring compounds which can give the water a brownish tint. Some fish live in tannin rich water which is often referred to as "Black Water". For the fish which live in these conditions the water is always very soft and acidic and this makes the best type of water to use when spawning the species. As a bonus tannins have both an antibiotic and fungicidal effect as well as cutting out some of the light.
You can create tannin rich water simply by filtering the water through aquarium peat, adding some bogwood or oak wood to the tank, adding a few Indian almond leaves to the tank or by using a commercially available black water extract in the water.
Fungicides, in the form of methylene blue and others aren't in my opinion necessary. The healthy fertile eggs have their own antibacterial and fungicidal properties and in good conditions they will usually remain healthy. Infertile eggs and other dead eggs will succumb what ever you add to the water.
Unless you are planning a commercial venture in fish breeding there will be more than enough eggs hatch for almost all hobbyists in most cases and trying to save a few extra ones is in most instances pointless.
How often do we see it written "get six young fish and let them pair up on their own then once you have a pair sell the others"? The trouble with this advice is that it leads to chronic inbreeding very quickly. If I went to a shop and bought the said six young fish, let them grow, obtained a pair and then bred them and later on I sold the brood to a shop. Then in walks the next person who wants to breed them and buys six of the brood and repeats the cycle. It won't be very long before inbreeding problems start to occur and this will show in the form of slightly deformed eyes, bent spines, missing operculum and so on.
To overcome this it is better to obtain your breeding stock either as wild fish if possible or to buy them from different places and at different times in order to minimize the chances of the fish being related.
Should fish be selectively bred? Unless you are breeding a domesticated 'fancy variety' such as Fancy Goldfish, Betta or Guppies for example then in most cases it is better not to.
But if you choose the 'best male' and the 'best female' probably meaning the largest and most colourful ones then this is a form of selective breeding which will ultimately produce a strain of fish which are abnormally large and abnormally coloured for their species and there is also a risk of introducing an undesirable trait into the line too.
It is far better to either net the fish to be bred at random from a tank of young, healthy and unrelated individuals or to let them pair up on their own if that is what the species in question does.
When breeding fancy varieties the very opposite of what is mentioned above takes place. The fish are deliberately bred with close relatives usually father x daughter or mother x son in order to try and 'fix' desirable traits into the line. This obviously can lead to problems of inbreeding within a few generations, to counter this most breeders have a few unrelated lines of the same variety on the go at the same time and every few generations a fish from one line is x bred with a fish from a different and unrelated line in order to get a new mix of genes. Doing this will slow down the effects of inbreeding for many generations but it won't stop the problem entirely and it is one of the reasons that fancy bred fish aren't as robust as normally bred fish.
Hybrids should never be sold on or bred deliberately unless it is to create a new fancy strain of fish, surprisingly a lot of the Swordtails and Platies we see today are actually hybrid fish which have been deliberately bred in more vivid colours or to have fancy fins and tail. But in most instances it isn't desirable.
Malawi cichlids are notorious for hybridising and occasionally these fish are sold on as being something else other than a hybrid especially if the hybrid has a passing resemblance to a real species. This eventually leads to the hybrid being bred with another fish of a true species and potentially contaminating a whole line of that species in captivity. Which in turn leads to what we now see in many fish stores a tank full of 'miscellaneous Malawi's' which are dull grey fish of varying shapes and sizes with the odd flash of blue or yellow left to show for their once former glory. If you accidentally breed some hybrids please don't allow them to leave your hands.
It goes without saying that you should only use parents which are in complete good health. They should be free from parasites and virus infections because either or both could be passed on to the fry. They also need to be in very good physical shape too because the female especially has to put a lot of her resources into producing the eggs and to use a female in poor condition could result in her death.
The other problem with fish which aren't at their peak is that they will produce inferior eggs which are smaller and the males could be less fertile and both of these traits will be reflected in the quality of the fry.
Young fish which have almost reached adulthood but haven't quite reached their full colour or their full size are at their most fertile stage in life and this is the best time to breed from them.
The female fish will find spawning quite stressful, she may get quite battered by the male and producing the eggs will use up a lot of her stored resources.
To help to minimize this and to help her produce a large healthy brood extra protein should be added to her diet. For this live food takes some beating. Alternatively frozen or freeze dried food can be used with almost the same results. Personally I have had very good outcomes when using freeze dried food, it's true that a majority of fish won't eat freeze dried food to begin with but if you persist in offering it in small amounts then very soon the opposite is true and the fish will eat all that is offered. Diskusin is one such food, often ignored to begin with the fish soon develop a taste for it and I have found it to be one of the very best conditioning foods available. It is made up into blocks and it contains a large variety of freeze dried ingredients.
Correct feeding is absolutely paramount to the success or failure of the whole exercise and it is worth making the extra effort over in getting it right
Spawning triggers are environmental changes which tell the fish it is the optimum time for spawning when there will be the right kind of food and conditions to maximize the survival chances of the fry. These spawning triggers take many forms, with feeding which encourage egg production being one of the main ones for a majority of fish species.
Temperature is another key one, most fish will start to come into breeding condition with a slight rise in temp while others such as Corydoras species are the opposite and a slight lowering of temp will usually
do the trick.
Changes in water chemistry, water changes in the aquarium, daylight hours and so on all have a part to play and vary from species to species. In order to get the best results you will have to research the particular species which you are hoping to spawn.
(No one said it had to be easy).
This really depends on the species, sometimes there are elaborate displays, sometimes elaborate spawning sites or nests are built and sometimes the spawning involves little more than the male apparently chasing the female and spawning as they go.
Anabantids - Generally build bubble nests, these are built and guarded by the male, other males are chased away while passing females are initially treated to a courtship display during which time they are assessed.
If they are ready to spawn the pair will meet below the bubble nest where spawning takes place, the male alone will catch the falling eggs and place them in the bubble nest after spawning the female will be treated as an intruder and chased away as will any females which don't respond properly to the males initial advances.
Some Anabantids are mouth brooders, this is where one of the parents picks up the fertile eggs into its mouth and stores them in a special brood pouch, in most cases it is the female who does the brooding but there is the odd exception to this.
Barbs - Barbs lay adhesive eggs scattered all over fine leaved plants or an artificial spawning mop. The male drives the female all around the tank for quite a while until all the eggs have been laid. There is no parental care and the adults may even start to prey on their own eggs.
Corydoras - Female Corydoras are larger than males it isn't unusual to see to male Corydoras breeding with a single female. They will use a solid surface (often the side of the aquarium) as a spawning site. There is no brood care and although they aren't generally avid egg eaters they will occasionally eat their own eggs.
Tetras - These can be quite tricky to breed, in most instances they will lay adhesive eggs over fine leaved plants. In most cases they won't protect their brood and will eat their own eggs.
Danios - Can be quite easy to spawn depending on the species. They lay non-adhesive eggs which fall to the floor, again there is little in the way of displaying but simply the male driving the female around the tank and spawning as they go. The eggs will be preyed upon by the parents if they get a chance.
Cichlids - This very large group of fish has a number of different breeding strategies, some are mouth brooders, cave spawners, nest builders and so on, they lay both adhesive and non adhesive eggs but almost all cases one or more of the parents will savagely defend its brood. They sometimes go through elaborate displays, fights, in order to attract a mate and in lots of cases they will defend their territory against all other fish. Seeing a pair of Cichlids raising a brood of fry is one of the most spectacular sights in the fish keeping hobby.
Livebearers - Probably most people are introduced to fish breeding through livebearers than any other fish. The males have a specially developed anal fin which is modified to allow internal fertilisation to take place.
The eggs are stored inside the female until the fry have hatched and are at the free swimming stage. In most cases the brood isn't connected to the female in any way as in mammals although there are exceptions even to this.
There is usually a very brief courtship where the male extends and vibrates his fins and then quickly mates with the female before moving on. Livebearers don't exhibit any brood care
The female in particular might be in a run down condition trough the efforts of spawning. If possible return her to a quiet tank alone, keep her well fed to build her back up, treat her with a mild aquarium antiseptic so that any small injuries and split fins will have time to heal before returning her to a tank with other fish.
In the case of some cichlids like Apistogrammas it might be the male in need of some TLC.
In the majority of cases there is little option and you will need to raise the brood without the parents being involved, this is because the majority of fish don't have any instinct to care for their offspring and would instead pose a serious threat to them. Most Cichlids are capable of brood care but some domesticated strains do seem to struggle a little and seem uncertain about what to do. They do seem to be able to learn though and although the first couple of broods might be lost it is worth persevering because seeing this when it is all going right is a sight worth seeing.
Personally I prefer mouth brooding species to be allowed to raise their own fry but in most other cases I think artificially raising the fry does have it's advantages.
Once the eggs have been laid and the parents removed their is little to do apart from wait. Try to place the filter or air stone in such a position that it helps to create a very gentle current over the eggs, this will ensure that the eggs have good oxygenated water flowing gently around them and this could help to increase the hatch rate.
Lots of people recommend using some type of fungicide at this time with the most common choice being methylene blue. I have used this in the past and I have noticed that when it is used at the recommended dose it stains the eggs blue. It is also a powerful disinfectant which kills the filter bacteria. Since using no fungicides I have not noticed any difference in hatch rates.
Some eggs do fall victim to fungus but these are probably the dead or infertile eggs which wouldn't hatch anyway. Neither do I attempt to remove these failed eggs because most of the time I made it worse when trying to do so, healthy eggs would get dislodged or the infected egg would disintegrate and end up being spread all over the healthy ones.
Healthy eggs do have their own fungicide and anti bacterial properties built in, if they didn't then quite simply fish would be extinct. Even with some egg losses there will be more than enough fry left for the average hobbyist to raise.
Apart from some Killifish, Livebearers and some Rainbow fish the overwhelming majority of fish hatch at a very early stage in their development and they remain very helpless.
The fry don't need feeding at this stage because they are sustained by their yolk sac and they won't attempt to eat until it is all used up. If the fry are easily visible you will see the yolk sac becoming a little smaller each day. Once these reserves are gone the little fry will start to search for food and this is where your work begins.
The fry of most egg layers can be quite tiny compared to livebearer fry. This makes finding suitable food quite difficult, in most cases they will be far to small to eat any type of flake food even if it has been crushed up.
Very small fry may need a liquid food to begin with, Liquifry has been around for years and most good fish stores sell it. Liquifry or similar does two things, it adds very tiny food particles to the water and it encourages the growth of infusoria which is a mixture of single celled organisms which even the tiniest of fry can prey on. To get the best out of liquifry it is best to add it to a little water and shake it until it is evenly dispersed and then add it to the tank, otherwise it has a tendency to stay congealed and might pollute the tank.
Take great care not to over feed the fry since any dip in water quality at this stage could prove to be fatal to the fry. Once the fry are feeding and growing other items can be added to their diet.
Once the fry are eating and growing you can begin to add more to their diet. Micro worms and Brine Shrimps are the two most widely used foods with a proven track record for the next stage. The fry will generally accept both of these without any trouble, along side these two you can begin to add some prepared food which has more variety and so helps to create a balanced diet. I use ZM fry food which goes all the way down in particle size to that of infusoria so even the tiniest of fry can manage it.
If the fry are raised on mainly Brine Shrimps I usually start to add crushed flake food to their diet at around five weeks old and by seven weeks they almost always accept flake food without any problem. If this isn't done some fish like Dwarf Cichlids and Killifish may refuse to accept flake food later in life and this makes their care more complicated. The fry will often be seen all pecking at the sponge filter as they grow and this is one of the main advantages of using one in a fry tank.
Water changes make as much difference to the fry's development as does good feeding. Very young fry shouldn't need any water changes until they have been free swimming for at least a few days. Start off very gently and change no more than just half of a jam jar full of water from a 10 gall tank.
Watch how the fry react to this, if they show any discomfort or odd behavior then leave it a while longer before trying again. In most cases the fry will carry on as normal and the next water change can be a little larger. Keep up with this gradual increase until you are changing about 10 to 15% of the water daily. Although this might seem excessive you will notice the difference it makes to the fry's growth. If the fry are stunted at this stage they will never make it up later in life. If you have made it this far don't blow it now for a little extra effort.
Don't be greedy and try to raise one or two hundred fry in a 10 gall tank, it can't be done. It is far better to grow on 30 good quality fry than 100 runts. Some fry will be deformed and ill equipped to deal with life, these fry should be culled as soon as they can be picked out. As the brood develops others can be picked out too until you have no more than you have the space to raise properly and that you can easily sell on. Remember in nature a pair of fish may spawn several times and lay a few hundred eggs each time but out of all those eggs only two fish need to reach adulthood in order to keep the population stable.
Lots of local fish stores will be keen to buy the fish from you provided that you have brought them up well. They will look at the size of the fish, in most cases depending upon the species they will expect the fry to be at least one inch or more in size and no more than twelve weeks old (and an experienced eye can spot these things). They will also look for a fairly even size among the brood unless it is a species where there is a marked difference in size among the sexes.
Uneven growth rates occur when the fry are kept crowded or water changes are insufficient and this will reflect on your breeding skills and a poor brood might be rejected.
There is also a question of numbers, the last thing a shop wants is to end up with to many of one species which they could end up being stuck with, neither will they appreciate it if you flood the area with a single species by selling to lots of different shops in an area (and they'll remember it next time you have some to sell).
This is another reason to grow only around 30 to 40 good fry instead of 100s. In all probability you won't make a fortune from the fry, indeed you might only break even but that isn't the reason for breeding fish as a hobbyist. It should be done out of interest, for the challenge, to learn something and for the deep sense of satisfaction you will get from it.
Wild fish are increasingly at risk for all kinds of reasons, by breeding good quality fish at home you will be helping to reduce the impact our hobby has on wild fish stocks. It is fun too.