In an aquaponics system, the marital bliss uniting the fish system with the plant system is referred to as being ‘coupled’, meaning the water exchanged in the fish tank is the same water that, once properly filtered, flows to the plant system, which then returns to the fish tank. This makes aquaponics recirculating. Not only is this union recirculating, but it is also what separates aquaponics from hydroponics. An aquaponics plant system is organically fed nutrients naturally by filtered and converted fish waste.
When running decoupled, a barrier divorces the plant and fish system, and the water from the fish tank gets filtered, converted, and returned to the fish tank. The plant system is now considered to be running hydroponically due to the nutrients being added to the its isolated water supply.
What Is the Difference?
For a decoupled aquaponic system, the potential to re-couple the system is always an option. Thus, an aquaponic decoupled system needs to add organic fertilizer into the plant’s water supply. This ensures that when the day comes for the system to be coupled, the plant system’s fertilizer-rich water can safely mix with the water in the fish system. There is no build up of inorganic nutrients.
A hydroponic system requires soluble inorganic and synthetic fertilizer to feed the plants. These are referred to as fertilizer salts, commonly composed of ammonium nitrate, potassium sulfate, magnesium sulfate, and calcium chloride. Not all of these fertilizer salts are absorbed by the plants’ roots. Those left unabsorbed remain in the water after the water evaporates or is lost to plant uptake. The subsequent salt build up accumulates in pipes and obstructs the water’s ability to channel new fertilizer to the roots. This leads to the system’s water needing to be drained.
In aquaponics, biodiversity is high. This invites one of two organisms: pathogenic or opportunistic. An aquaponics system generally begins without any aquatic organisms. However, over time, beneficial microorganisms develop and outcompete the pathogenic organisms and the system becomes healthier and more resilient to disease.
Supplemental Nutrients in Aquaponics
Fish feed doesn’t always supply all the necessary nutrients plants need. Microminerals not made available to the plants from fish include calcium, potassium, and magnesium. A common absent micromineral in aquaponics is iron, which is either not present in the food or is in an oxidized state in the water which is not bioavailable for plants.
These minerals are administered most effectively as foliar sprays. Microminerals must be administered in minimial amounts to increase operational sustainability. We also utilize amino acids and humic fulvic acids that help naturally chelate the minerals and convert them into a biologically available form for the plant. More on this can be found in our Aquaponic Farm Management Plan
Unfortunately, there aren’t many sources consisting of all the necessary elements our plants need all at once, but there is one sustainable source we know exists: Oceans. Ironically, it is fermented or diluted seawater that can be used as a foliar spray, as long as it is mixed proportionally according to the chart below.
Decoupled Plant Fertilizer
We recommend using Espartan to feed your plants when your aquaponics system is decoupled. Espartan is liquid organic matter developed from vegetable concentrate remains and is rich in organic matter (33.50%) and Fulvic Acids (19.00%). The only drawback to Espartan is due its high amount of tannins, it will darken the water a brownish color. However, Espartan is fish safe so when the time comes to recouple the system, the water will mix safely.