How to achieve high rate of fry survival
Guide by Mick, keeping fish since 1976
The percentage of fry survival can be a critical factor in the fish breeding business and for many hobby breeders, it is also important as nothing can be more upsetting than spending the time on preparing the project just to lose most of the fry, this article will cover factors that are required by fry of various species so hopefully after reading this it will give you some pointers on how to achieve a better success rate and in turn gain more satisfaction in the hobby.
When breeding fish there are many aspects that have to be taken into consideration such as the breeding patterns of the fish, are they live bearers or egg layers, do they make good parents etc. so always research the species before attempting a breeding program to give you a good start and it will also make sure that you have the equipment required to raise batches of fish from eggs right through to mature specimens. Experience will come in time so always be patient and if things don't work out straight away, research on the net or with a good reference book, there is plenty of advice out there on forums etc. and you can ask as many questions as you need to via the comments box placed at the bottom of this article.
So the best place to start has to be how do you prepare a tank for growing on your fry and offering them the best chance. I made a major mistake when I first started fish breeding, due to the large number of fry initially I thought that a larger growing on tank would provide them with more room to grow, unfortunately fry can use a lot of energy swimming around the tank looking for food, if you use a small tank the food will be in front of them and the energy can then be saved thus resulting in a better growth rate. I always found a 2 foot tank ideal which will require filtration as fry demand the highest water quality. For this purpose I always used air driven sponge filters, the sponges prevent the fry from being sucked up into the inlet pipes thus causing more mortalities, the water flow can be turned down to a gentle flow and the sponges are very easy to clean on a regular basis, using a double sponge filter allows you to rotate the cleaning process thus keeping the filter effective all of the time. The first fill of the growing on tank should be completed by using water from the breeding tank so that when the fry are moved, they will not be susceptible to any form of shock due to changes in the water parameters.
Any fry demand high water quality so regular water changes are a must, this will involve performing daily percentage changes to keep the water as clean as possible.
Some fry can be raised with their parents but there are many species of fish that will eat their own young, always research this-many live bearers are guilty of this but remember there are also some species of fish that need to be with their fry such as Discus, these fish provide a “milk“ for the first few weeks of the fry's life and it is extremely beneficial to the growth of the brood.
So the growing on tank is set up we can feed the fry, this is not always the case. As the name suggests live bearers produce fry that are miniature replicas of their parents in most cases, these fry will accept food immediately and often eat the same diet as their parents. Fry only have small mouths so this food needs to be reduced in size i.e. flake food should be crushed so that they can digest it properly. However do not add food to the tank with fry that have hatched from eggs, when they first hatch they will consume their yolk sacs initially so they will not be interested in any other food, this will just spoil the water if it is left uneaten. Once the yolk sac has been consumed the fry will then become hungry and search for food. At this stage they are classed as free swimming and now you can start to supply them with regular meals. The golden rule is that small meals on a regular basis are much more beneficial rather than feeding them twice a day with larger meals, not only do they have small mouths but also small stomachs so they will become full very quickly. They require small foods, Infusoria is ideal, this is easy to digest as is newly hatched brine shrimp, older brine shrimp lose their nutritional value so only feed shrimp that are freshly hatched. There are commercial feeds available but home grown food saves on the budget which we all agree with at the end of the day. Any uneaten food must be syphoned out of the aquarium, if it is left to decay the water quality will deteriorate very quickly meaning more mortalities in the long term.
This is now where it can start to get complicated, it's a fact of nature that some of the fry will grow and develop quicker than others, after a few weeks you will have some fry larger than the others and these will need to be size graded, the larger fry can intimidate the smaller fry and in some cases they may even turn cannibalistic towards their fellow tank mates. Size grading means that the larger fry need to be moved into a separate growing on tank giving the chance for the smaller fry to catch up which they will do in time. Any deformed fry should be culled, not a nice aspect to the hobby but it prevents offspring with weaker genes passing on this trait to future generations so overall it is good for the species and means that high quality fish are maintained. As the fry grow the size of the growing on tank should be increased to suit, always allow the fish the same room, move the young to larger tanks in stages to get the best results.
As long as the tanks are kept spotlessly clean and the general guidelines are followed, then you should have high percentages of healthy young fish, taking short cuts is not a good idea as this will lead to future problems.