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Australian scientist Dr Wilson Lennard has developed a new domestic aquaponics system design model for those people who wish to design and build their own backyard media bed aquaponics systems.

Several weeks ago, he released The Backyard Systems Design Tool (which comprises a calculator and explanatory notes) which allows the user to size the media-filled grow beds based on a fish feed to plant ratio, bio-filtration requirement and solids mineralisation.

For those who are already operating grow bed AP systems, the model will allow the user to reconcile the relationship between grow bed area, stocking density and feeding rates.

Both Australian aquaponics kit makers commissioned reports from Dr Wilson Lennard – to see how their wares stacked up against his Backyard System Design Tool.

Both Backyard Aquaponics and Practical Aquaponics expressed satisfaction that the model (and the reports) vindicated their systems.

The kit makers posted their reports – both of which stated that, for each of the systems tested….

“As long as the suggested maximum fish culture density isn’t exceeded, the system will work to bio-filter all dissolved fish wastes (eg: the nitrification of all ammonia), to grow all plants with the required amount of nutrients for those plants and mineralise all solid fish wastes that the fish produce.”

Since the volume of the fish tanks and the area of the media beds was fixed, the only variables were the daily feed rate (set at 1%) and the feed protein level (set at 45%).

These variables were, in effect, the conditions upon which the kit assessments were based in that, if the operator of a kit maintained a daily feed rate of 1% of the fish biomass (using a ration with a 45% protein level) then they could expect the system to function appropriately.

Both BYAP and Practical Aquaponics have always claimed (not surprisingly) that their kits worked…..so what’s changed.

  1. They now have an independent assessment of their products which supports that basic claim…..within clearly defined criteria.
  2. The assessments have been undertaken using a model which has been developed by a scientist with direct experience of aquaponics……so anecdotal input and guesswork have been replaced by accepted scientific and engineering principles.
  3. Questionable stocking density claims (inasmuch as they attached to basic flood and drain systems) have now been moderated to something much more realistic.
  4. Claims to operating effectiveness can now be linked to measurable criteria like media bed surface area, daily feeding rate, feed protein level and maximum fish culture density.
  5. Through the generosity of its developer, the Backyard System Design Tool is available to everyone – so prospective purchasers can confirm basic performance claims relating to kit systems and make better-informed decisions.
  6. The Explanatory Notes for the Backyard Systems Design Tool provide maintenance recommendations that, if adopted, will considerably enhance the performance of the basic flood and drain system.

The Backyard Systems Design Tool is still being fine-tuned by Dr Lennard but, it has already achieved something of real importance.

It allows those who found beauty in the simplicity of the basic flood and drain aquaponics system to stand in the same room with others (like myself) who had concerns about exaggerated performance claims and questionable husbandry practices.

Advocates of the basic Speraneo approach can continue to say “See, it works” and those who prefer a broader approach can continue to say “Yes, it does……subject to certain conditions” and we can both be right (which is apparently an important part of the human condition).

Now, we all have a datum to which we can attach.

Dr Wilson Lennard is to be congratulated on his work in developing the Backyard Systems Design Tool and for making it available to the broader aquaponics community.

While he acknowledges that the model is still evolving, it’s a giant leap forward.

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