Agri Kultuur August / Augustus 2018 | Page 17

(called biofilters) are actively encouraged and inoculated to contain beneficial bacteria such as Nitrosomonas and Nitrobacter, which convert organic material from fish waste into plant-usable nutrients. Biofilms contain both dead and live microbes and a variety of secreted compounds such as polysaccharides, proteins, DNA, lipids, minerals, and other components from the environment, all of which form complex and resistant layers. Biofilms begin life as free –floating bacteria that are common in most water supplies. These bacteria attach to surfaces and are not particular about where they take up residence. In plant production systems, bacteria are often attracted to the organic material contained in root exudates that act as a food source, thus roots are often rapidly colonized. Bacteria in Aquaponics Many people look at aquaponics systems and all they see is fish and plants. Much is written about this and many people define aquaponics as the “combination of fish and plants”. The fact is that there is a third, and equally important group, whose management is often completely ignored: bacteria! While most people acknowledge bacteria, usually AgriKultuur |AgriCulture the nitrifying genera, as being necessary to aquaponics systems there is often little acknowledgement of the true importance of many other species of bacteria and almost no methods are deployed for their management. Aquaponicists will often talk about nitrifying bacteria and while there are several genera of bacteria that will oxidise Ammonia to Nitrite and Nitrite to Nitrate the most common genus mentioned is Nitrosomonas and Nitrobacter respectively. Positive bacteria have four main benefits for areas like fish intestine lining and plant root tissue. 1. Preventing bad bacteria from taking hold. If the surface is already occupied by a good bacterium then the bad bacteria cannot take hold. 2. Promoting surface health. They can aid in breakdown of organic material that may get on the surface as well as actively assisting tissue health. 3. Being antagonistic to bad bacteria. Many positive bacteria do not only prevent bad bacteria taking hold but actively antagonize bad bacteria, so they are removed from the environment. 4. Improving nutrient uptake and health. 17