Agri Kultuur August / Augustus 2018 | Page 13

Plants grow rapidly in response to dissolved nutrients that are excreted directly by the fish or generated from the microbial breakdown (mineralization) of fish wastes. In closed recirculation systems with very little daily water exchanges (less than 5%), dissolved nutrients accumulate and approach concentrations that are found in hydroponic nutrient solutions. Dissolved nitrogen, in particular, can occur at very high levels in recirculating systems. Fish excrete waste nitrogen directly into the water through their gills in the form of ammonia. Bacteria convert ammonia to nitrite and then to nitrate. Ammonia and nitrite are toxic to fish, but nitrate is relatively harmless and is the preferred form of nitrogen for growth of higher plants, such as fruiting vegetables. It is the symbiotic relationship between fish and plants that makes the consideration of an aquaponics system a reasonable system design criteria. As existing hydroponic and aquaculture farming techniques from the basis for all aquaponics systems, the size, complexity, and types of foods grown in an aquaponics system can vary as much as any system found in either distinct farming discipline. AgriKultuur |AgriCulture What is a Microbe? A microbe, or “microscopic organism,” is a living thing that is too small to be seen with the naked eye. We need to use a microscope to see them. The term is very general. It is used to describe many different types of life forms, with dramatically different sizes and characteristics: • Bacteria • Archaea • Fungi • Protists • Viruses • Microscopic Animals Under natural conditions, a microorganism rarely exist in isolation. Even when a single microbial cell is successfully isolated in the laboratory, the individual normally will multiply and form a group (a clone) of similar individuals called a population. Typically, in a natural environment, numerous populations of different character coexist. The microbial populations that live together at a particular location, called a habitat, interact with each other to form a microbial community. The 13