Components of a Fish Farming System
Business models for fish farming, or aquaculture, include high-intensity production in controlled conditions, use of existing ponds and waterways, and production in cages submerged in large bodies of water or designed to complement agricultural operations. If you’re fortunate enough to be able to supply your tanks with an unpolluted source of flowing water, you can greatly simplify your layout. This is a rare amenity, and you’re more likely to be growing in a closed system where water is kept mechanically aerated and conditioned. Fish farms require a lot of energy to operate, so are good candidates for on-site solar generation. They also produce nutrient-rich waste water that saves farmers money on fertilizer and soil amendments when used to irrigate crops.
Read also: The future of fish farming
Different types of fish mature at various rates, so your choices in the number and size of tanks vary with the type of fish you plan to grow. At minimum, you need a tank for newly hatched fish, called fry, a tank for fingerlings and at least one tank for growing fish to finish size. Depending on the water source you plan to use, you may also need a tank for conditioning replacement water. If you plan to raise fish food species on-site, you’ll also need a pond or a tank. Plastic, concrete, metal, wood, glass, rubber or plastic sheeting are all used as tank materials; your main considerations in choosing the material for any type of tank is its ability to hold water, resist corrosion and remain non-toxic to fish. For a healthier fish crop, choose a smooth material that won’t scratch fish that brush against it, and which doesn’t have pores to retain dirt and bacteria.
Water Filtration and Conditioning
A closed system of tanks needs to have fish waste and excess food particles constantly filtered out to prevent overgrowth of bacteria and toxins. It needs to be free of chemicals, such as chlorine, and kept at the proper pH for the species of fish you’re growing. Filtration can be achieved with a combination of biofiltration and mechanical filtration. Biofiltration in a closed system uses beneficial bacteria to break down ammonia and nitrates. Mechanical filtration is done by pumping water through filters to remove organic particles. Precondition water in a separate tank to remove water treatment chemicals and toxins and to adjust pH.
Fish need oxygen to survive and plenty of it to thrive. Poorly aerated water or water that contains a high algae population can cause fish to asphyxiate. Mechanical aeration, or oxygenation, takes the place of waves, wind and flow to keep water moving so that it circulates to the surface and picks up oxygen. Types of mechanical aerators include air stones, pure oxygen injectors and pumps that circulate water between the bottom of the tank and the surface. The percentage of dissolved oxygen in the water is monitored at all times, so a dissolved oxygen meter in every tank that contains fish is indispensable. Some farms use floating water plants to help oxygenate water and shade it to minimize algae growth.
Most fish are evolved to live in waters of a certain temperature range. They may be able to survive in water outside their preferred ranges, but are unlikely to truly thrive and grow large in those conditions. Regulate temperature according to your fishes’ needs with immersion heaters, gas or electric heating units, heat exchangers, chillers or heat pumps.
Read also: Understanding fish nutrition and feed
Water and Fish Transfers
You’ll need a way to move fish from one tank to another and a system for replacing water that has evaporated or must be replaced for tank hygiene maintenance. Each tank must have gates to facilitate the transfer of fish from one to the next. Even the most efficient system is still not capable of retaining all its water or of keeping water with hundreds of full-grown fish in it immaculate, so you’ll also need inlet and outlet gates to move fresh water in and dirty water out. Pumps are essential to this, especially if you must completely drain and clean a tank that has become too dirty or infected with a pathogen. You’ll choose from among propeller pumps, deep-well turbine pumps and centrifugal pumps. Water can be moved though either canals or pipes. You must be able to fully close gates to control conditions in individual tanks.
Contributed by: Billie Jo Jannen
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