Reproductive Failure 

In other words: Help! What am I doing wrong? 

Breeding fish whether by accident or design can be highly addictive, very frustrating and often highly rewarding. For novice breeders there is a wealth of information around about breeding a wide variety of fish. But what happens when something goes wrong? Forum posts with the word HELP in the title are the most common type of posts on my site, and for this reason, and because I feel I owe aquarticles for all the articles they have made available to me I decided to write a bit about what can cause things to go wrong.

Reproductive failure can occur at any stage in the breeding process, from first introducing the fish right through to the death of the fry, and sometimes even prior to you taking the fish home in the first place.

The first stumbling block that people often encounter is failure to spawn. No, your Neon tetras will not spawn in a community tank, those are snail eggs! You need to have the right setup for the species of fish that you want to breed, the correct water chemistry, quality and temperature and spawning triggers if the species demands them. If you don't provide these basic factors you are doomed to failure.

Having the right setup often involves a separate spawning tank of the right size containing the correct substrate, or none, depending on the species, suitable spawning medium and appropriate lighting. And if the fish require spawning triggers you must provide them. Spawning triggers can range from a simple change in temperature, to a complete simulation of the dry and rainy seasons encountered in tropical regions. To understand how spawning triggers work have a read of the excellent article titled 'Dry and Rainy Seasons in the Tank' by Kristian Adolfsson on Aquarticles, it also shows the lengths some aquarists will go to in order to spawn their fish!  

Water chemistry is often ignored when it comes to novice breeders, you can't just stick two fish in any old water and expect them to get on with it, you need to get a full test kit and know how to use it. If the water is wrong the fish won't spawn regardless of anything else you might do. Also bear in mind that the quality of the breeding stock has a direct bearing on the viability of the spawn, and the quality of the breeding stock is the direct result of the conditions in which the fish have been matured.

So you have taken care of the environment and the fish still won't spawn? To begin with, you must make sure you have a member of each sex, some fish can be hard to sex even for experienced fish keepers, so this advice isn't quite as silly as it sounds. Sick or stressed fish won't be interested in spawning, (so try to not walk up to the tank and peer in every two minutes!) nor will victims of aggression, although for some fish a bit of rough and tumble during spawning is normal. On occasions the eggs may fail to develop in the ovary. This is commonly caused by incorrect water conditions though it can also be linked to diet, prospective parents must be in top condition prior to spawning.

Attempting to use fish that are too old or too young is another  cause of reproductive failure. In nature, female fish will seek out a male in his prime, as breeders, we often need to do the seeking for her. Males that are too young or too old may not be able to produce viable sperm, so even though they may appear to go through the motions, any eggs produced may not be fertilized. This can cause the eggs to either fungus, or be eaten by the parents. With young females please remember that each episode of egg/fry production will take it out of the female and can restrict her growth. My midwife once said to me "Babies are like parasites, they take what they need from their mothers regardless of whether the mother has it to give" the same can be said about developing eggs and fry. With species that require the female to be separate from the male, but in view of him such as Betta's, you must ensure that the female is ripe. If the eggs aren't developed sufficiently to be laid she won't be ready to spawn and will be perceived as a threat by the male. 

Some territorial fish won't spawn if they are unable to secure a suitable territory, others may require the addition of a target fish in order to get the male more interested in his female and in his territory. Nervous fish may sometimes need the reassurance of a dither fish before they will relax enough to spawn. These are the tips and tricks of the hobby and known to work on some species, so if everything else is right it might be worth trying one.

The fish have spawned but there's a problem with the eggs?

There are two main reasons why eggs can fail to hatch, the first is...... can you guess? Yep, water quality! Books, articles and web sites don't go on and on about it for nothing you know! Poor or incorrect water quality for the species can not only cause the failure to spawn in fish, If they do manage to spawn, it can also affect the viability of the eggs causing them to not develop properly and fungus. The viability of the milt produced by the male can also be adversely affected. Quite often with some species, the eggs are removed to another tank for hatching, in most cases care must be taken to avoid exposure to atmospheric air as they can rapidly dry out and die. The water in the hatching tank must be of the same chemistry and temperature. Exposing the eggs to an increase in hardness can cause the development to either fail or the exterior of the egg to become too tough for the fry to break through. Softer water can cause the eggs to collapse. Exposure to a sudden change in temperature can also halt the development of the eggs causing them to fungus.

Sterility in one or both fish is the other main cause of eggs failing to develop, though in some Cichlid species it is not uncommon for two females to pair off if there is no male present, needless to say the eggs will be infertile. As I have already mentioned, using males that are too young or too old to produce viable sperm will often lead to the eggs failing and with normally parental species being eaten. This is not a habit you want to promote as it can lead to a long term behavioral defect (more on that later!). Disease can also play a role in the functional sterility of fish. Tumors and fat deposition from feeding brood stock with the incorrect diet can have a direct effect on the gonads causing sterility, as can certain chemical remedies, the most reported being from remedies containing Malachite Green.

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