Agri Kultuur September 2014 | Page 43

Photo: www.myaquaponic.files.wordpress.com Photo:: www.greatlakespremacultureportal.com A basic set-up for an aquaponic system. excrete waste and respirate ammonia into water. Ammonia is toxic to fish in high concentrations, so it has to be removed from the fish tanks for fish to remain healthy.  Ammonia-laden water is processed to harvest helpful types of bacteria such as Nitrosomonas and Nitrobacter. Nitrosomonas turns ammonia into nitrite, while nitrobacter converts into nitrate- both of which can be used as plant fertilizer.  Nitrate-rich water is introduced to the hydroponically grown plants (plants grown without soil) plants which are placed in beds that sit on tubs filled with water, and the water is enhanced by the nitrate harvested from the fish waste. The plants' bare roots hang through holes in the beds and dangle in the nutrient-laden water.  The roots of the plants absorb nitrates, which act as nutrientrich plant food. These nitrates, which come from fish manure, algae and decomposing fish feed, would otherwise build up to toxic levels in the fish tanks and kill the fish. But instead, they serve as fertilizer for the plants. The hydroponic plants' roots function as a bio filter - they strip ammonia, nitrates, nitrites and phosphorus from the water. Then, that Aquaponics come in different shapes and sizes. This one represents a simple but effective medium sized system. clean water is circulated back into the fish tanks. Because fish waste is used as fertilizer, there's no need for chemical fertilizers. In fact, the only conventional farming method that's used to operate an aquaponics system is feeding the fish. Aquaponics System Requirements Many warm-water and cold-water fish species have been adapted to aquaponics systems. The most commonly cultivated fish in aquaponics systems are, however, tilapia which are tolerant of fluctuating water conditions, changes in pH, temperature, oxygen and dissolved solids. They also are in high demand - this white-fleshed fish is frequently sold in markets and restaurants. Plants which thrive well in aquaponics are leafy greens and herbs. The high-nitrogen fertilizer generated through fish waste allows plants to grow lush foliage. Lettuce, herbs and greens like spinach, chives, bok choy, basil, and water cress do well in aquaponics systems. Another major component of aquaponics is the water itself. Monitoring the water's pH, which determines acidity, is of the utmost importance to ensure safe levels for the fish. Water quality testing equipment is also important to ensure that both fish and plants remain healthy. It's also important to keep an eye on dissolved oxygen, carbon dioxide, ammonia, nitrate, nitrite and chlorine. Although the ratio of fish tank water to hydroponic product depends on fish species, fish density, plant species and other factors, a general rule of thumb is a ratio of 1:4 tank contents to bed contents. Basically, for every one part of water and fish, you'll want to have four parts plant and bed material. Some aquaponics systems are outfitted with biofilters, living materials that naturally filter pollutants out of water and that facilitate the conversion of ammonia and other waste products. Other systems feed fish waste directly into the hydroponic vegetable beds. Gravel in the vegetable bed acts has a bioreactor, a material that helps carry out the chemical processes of living organisms. Home Aquaponics Backyard gardeners can set up an inexpensive aquaponics system using recycled materials. For the backyard vegetable gardener, aquaponics can offer many benefits. These systems use much less water than a conventional garden, and you won't lose much water through evaporation. Your plant harvest definitely will be organic because you can't use chemicals - they'd harm your fish.