Tuesday 18 June 2019

Decoupled Aquaponics

Why Decoupled Aquaponics
Most aquaponic systems are single loop and fully recirculating. This means that the fish and plants exist in a single loop and share the same nutrient rich water. The reason these are the most popular is because they are simple to build and operate. But single loop systems are also a compromise because the plants, fish and bacteria must all be happy in the same solution. So for example, the temperature and pH levels must be maintained at levels that satisfy all the organisms, rather than being optimized for each.
pH is maintained in a range to satisfy fish, plants and bacteria in a single loop system
In a dual loop system, these parameters can be maintained optimally at different levels in each loop. Additionally, if something goes wrong, there are more options to address the situation without affecting everything in the system. So for example, if pests need to be treated on the plant side, it can be done without adversely affecting the fish.

How Decoupled Systems Work
A typical decoupled system consists of a stand-alone RAS (recirculating aquaculture system) loop and a hydroponic plant loop. The sludge from the RAS system is digested in the biological waste system which provides the nutrients for the hydroponic system. Using a digester makes the system more efficient because the nutrients plants need (aside from Nitrogen) are trapped in the solid waste. The aerobic digester (a fancy term for a simple tank with air-stones in it) mineralizes the solid waste, releasing the nutrients the plants need.

A Simple Decoupled System
A small decoupled system can be very easy to build and operate. If an AST bead filter is used, the fish loop is reduced to two components (fish tank and bead filter) because bead filter combines both bio-filtration and very efficient mechanical filtration. It also makes the system very easy to maintain and operate because it is self-cleaning. The following video shows simple the decoupled system can be with an AST bead filter.

The Heart of the System: AST Polygeyser Bead Filter
Although the video above shows a smaller endurance filter, the AST Polygeyser 3 cubic foot automatic backwash bead filter can be used to build a similar system that supports up to 60 mof plant area (900 gallon fish tank with up to 4.5 pounds of feed per day input).


  1. The pH requirement stated for plants in aquaponics is ALWAYS based on what is required for plants in hydroponics. However, pH has far less of an effect in terms of plant nutrient availability in aquaponics, to the point where if you operate at acceptable fish pH levels (i.e. approximately pH = 7.0) this pH is more than adequate for the plants. The misconception is that in hydroponics, acidic pH is required for broad nutrient availability for the plants, and it is therefore assumed, that aquaponic plants require the same. However, this is not true due to several differences between hydroponic and aquaponics. The largest difference is that aquaponics is not a sterile system and therefore, the present microorganisms assist the plants to gain access to nutrients and this means pH has far less of an effect. In addition, it is very easy to design fully recirculating aquaponic systems that provide the flexibility to be able to separate the fish and plant components and operate them individually when required. Therefore, the premises stated here to argue that de-coupled is a more flexible approach are not supported by the facts!

    1. Thank you Wilson for your helpful comments as usual. Can you link to any research on this topic? Decoupled systems would still have the advantage of running two temperatures correct?

    2. The decoupled would give more advantageous, the plant require 13 or more nutrients and these nutrients are not coming adequately ex pottasium..
      The nutrients which are not in proportion , we can supplement easily using organic nutrients ( sea weed ) or synthetic nutrients. Also, as temperature goes down , it affect fish and as well micro organisms.. the fish, micro organisms are very sensitive and it's challenge upkeep all time to keep all 3 organisms happy.
      Hydrilla India.. venkat


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