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Building from the initial explanation of aquaponics in Chapter 1, this chapter discusses the biological processes occurring within an aquaponic unit. First, the chapter explains the major concepts and processes involved, including the nitrification process. It then examines the vital role of bacteria and their key biological processes. Finally, there is a discussion of the importance of balancing the aquaponic ecosystem consisting of the fish, plants and bacteria, including how this can be achieved while maintaining an aquaponic unit over time.
Aquaponics is a production system that combines fish farming with soil-less vegetable production in one recirculating system.
Nitrifying bacteria convert fish waste (ammonia) into plant food (nitrate).
The same nitrification process that happens in soil also happens in the aquaponic system.
The most important part of aquaponics, the bacteria, is invisible to the naked eye.
The key factors for maintaining healthy bacteria are water temperature, pH,
dissolved oxygen and adequate surface area on which the bacteria can grow.
Successful aquaponic systems are balanced. The feed rate ratio is the main guideline to balance the amount of fish feed to plant growing area, which is measured in grams of daily feed per square metre of plant growing space.
The feed rate ratio for leafy vegetables is 40-50 g/m2/day; fruiting vegetables require 50-80 g/m2/day.
Daily health monitoring of the fish and the plants will provide feedback on the balance of the system. Disease, nutritional deficiencies and death are symptoms of an unbalanced system.
Water testing will provide information on the balance of the system. High ammonia or nitrite indicates insufficient biofiltration; low nitrate indicates too many plants or not enough fish; increasing nitrate is desirable and indicates adequate nutrients for the plants, though water needs to be exchanged when nitrate is greater than 150 mg/litre.
Source: Food and Agriculture Organization of the United Nations, 2014, Christopher Somerville, Moti Cohen, Edoardo Pantanella, Austin Stankus and Alessandro Lovatelli, Small-scale aquaponic food production, http://www.fao.org/3/a-i4021e.pdf. Reproduced with permission.