středa 23. dubna 2014

How to Breed Trouts at Home

Fish are an important part of the aquaponic system as they enrich the water with nutrients, which are used for plant's growth and the plant consequently clears the water for the fish. Which species can be bred at home? How fast will they grow and how many fish can be in there?

In the previous article I have discussed the choice of plants that will maximize the benefit of aquaponic farm throughout the year and simultaneously said plants were not high maintenance. However, fish are way more interesting part of the farm because the image of picking live rainbow trout and grill it the same evening after work is rather unusual opposed to growing a vegetable - that could be done by merely anybody.

The living part of the aquaponic system is not dedicated to fish only. In theory, any random water animal that eats and defecates into water can be used. Miniature aquaponic systems that are used for educational purposes usually works with crayfish.

These systems use Procambarus fallax (also known as Marble Crayfish). This species was probably created by unique genetic mutation since all the crayfish are diploid females. It means that the process of procreating goes without any need of male interaction. Diploid females lay eggs from which other diploid females are hatched.

You can imagine how can such an animal be harmful to environment – especially if it gets somewhere it should not be. Therefore its breeding is forbidden or strictly regulated in some countries.

It is ideal animal for aquarist beginners – it is unusually resistant mutant that can reproduce itself. It is fine in temperature ranging from 15 to 25 °C, it eats merely everything including vegetable and thanks to many legs and claws it is astonishing to watch while eating. You have to be careful about chlorine getting in the water though, as it is poisonous for crayfish.

Marble crayfish grows up to 13 cm in length. Because my aquaponic arm is primary about food I had to disregard this peculiar animal. Not because its meat is not delicious but I am not willing to debone those tiny bits.

If you are going to look up information about aquaponia then you can not miss the tropical fish called Nile Tilapia (Oreochromis Niloticus Niloticus). It it the second commercially most bred fish in the world, right after the carp. This is for several reasons:

It is an omnivore. It eats anything from vegetable to small fish. Due to the known fact that African rivers suffer from sudden changes of dry spells and floods the Tilapia can live in dirty water with low amount of diluted oxygen. On top of that, this fish grows incredibly fast. In period of six months you get two 250g fillets from a single fish egg. Its taste and quality is very similar to Czech pikerperch (very good fish).

However, the biggest plus of Tilapia is its reproductive ability. If you breed fish in artificial conditions and higher concentrations you will probably fail to reproduce them. Creating reproducing conditions is very hard – you have to put together a capable pair that will understand each other and prepare natural conditions by combination of food and temperature and sometimes it is necessary to change water in the tank regularly to make fish feel like it is a rainy season.

Tilapia on the other hand reproduces in artificial tanks. Plus it is a so called mouthbrooder. Mother keeps its offspring in their mouth. They take impregnated fish eggs in their mouth and they stay in until they are ready to live on their own. It protects small fish from being eaten by other Tilapia. Using Tilapias you can create a naturally reproducing swarm that needs only feeding.

The reproductive ability in artificial conditions really drew my attention and therefore I spent quite a time thinking about breeding Tilapia in the Czech republic. I was forced to drop the idea eventually because of its temperature requirements. Tilapia, as any African fish, is very sensitive when it comes to water temperature – it will survive in temperatures ranging from 14 to 28°C but the peek of reproduction is on the higher margin of that range while it perish in colder water.

Due to our climate conditions it would be both very demanding and expensive to keep water in the system warm enough. Since fish are cold-blooded animal its metabolism is accelerated and slowed down by the water temperature. Even a decrease of temperature by 5°C to 23°C causes Tilapia to grow half the speed than in normal conditions and its breeding will probably end up uneconomic. It is a shame though.

From variety of usable fish I chose three that you might know very well. First it a classic Czech carp. It grows quite fast, it is fairly resistant and is fine in water temperature around 0°C. It prospers the most at 24°C which is a realistic temperature over the summer. In these conditions can a 250 gram of sprouts reach up to 2 kilo a year. This will be my start-up fish.

Once the system runs smoothly with carps and I manage to keep the parameters stable I will immediately switch to Rainbow trouts. Although this fish is very sensitive to the water quality it is still less demanding than our common trout. This is why is the rainbow trout kept in large numbers at farms. A year sprouts can grow up to 400g during 6 months. Since trouts are predators they require a quality food with enough protein. In reward you get unbelievable sight of their aggressive feeding. Take a look at the video below and you will see.

The rainbow trout likes colder conditions – it handles temperatures from 0°C to 21°C, but it prospers the most at 15°C. I hope it will be possible to breed it all around the year with buying new sprouts from time to time. There is a risk of some very hot days during the summer but I have to finish the farm and test it first. For example – rainbow trouts are bred as a winter fish in the Australia. They enter the aquaponic system in autumn and are fed until spring when they replaced by tropical tilapias.

The last fish I would like to try in the aquaponia is the catfish. This predator is famous mainly for its record length and weight that reaches up to 100kg. You do not want to keep something this big in your garden but young catfish grow fast in warm water and its meat is delicious. They can eat practically anything using their big mouths as the pigeon in this video figured out.

The number of fish in the system is affected by the proportions of the tank and the amount of food that can be absorbed by plants every day. Usually it is a 60 - 100g of fish food a day to square meter of growth area. Well prospering fish will consume about 2% of their weight while half of the food will be turned into muscle mass and the other will be defecated into the system. These parameters can help to calculate maximal rough weight of the fish swarm. These breathtaking calculations are coming up some next time.

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