The Queenslander – an Aquaponics System that Really Works

In my previous post, I described the criteria that I apply to the design of an aquaponics system.

Upon reflection, I realised that the post contained an implicit assumption – that the system should actually work.

While this might appear to be a blinding flash of the obvious, the simple fact is that many aquaponics systems are dysfunctional – and most of those that do actually grow fish and plants still fall far short of their productive potential.

The simple explanation for the failure of these systems to function at peak capacity is that they are, quite literally, full of sh*t.

Our latest aquaponics system, The Queenslander is a best practice approach to system design and the culmination of everything we’ve learned about aquaponics.

The standard recirculating aquaponics involves the movement of water from the fish tank to flood and drain grow beds and then back into the fish tank (possibly via a sump tank).  This arrangement is simple to build and operate and it works……for a while.

Even cursory reading of my work will reveal my disdain for using grow beds to capture and process solid fish wastes.  While science and logical thinking is on my side, aquaponic fundamentalists persist with the myth that grow beds can be used as outhouses without consequence.

Cost effective fish production requires that we grow the fish as quickly as possible and this requires that we feed as much as the fish can efficiently convert.  To consistently feed at the optimum rate we need to be able to convert the waste products of that feeding while ensuring that oxygen levels are consistent with the needs of our fish.        

While this is relevant to any aquaponic system, it’s particularly critical for small backyard units.

Over several years, I’ve seen some very impressive filtration equipment that will do an excellent job of separating out solids but the devices all had one thing in common – they were expensive.  Very often, these filtration systems would cost more than all of the other aquaponics system components put together.

I’d also tested most of the less expensive options, like sedimentation and swirl tanks, clarifiers and trickling bio-filters.  While they all worked to some extent, they still demonstrated shortcomings when applied to smaller systems.

Anyway, the challenge that presented itself was to develop a cost effective alternative to the bog-standard (and often deadly) flood and drain aquaponics system.

While I’d like to say that outcome of my countless watery meditations produced a silver bullet, but it simply wouldn’t be the truth.

The simple reality is that designing an aquaponic system that really works is not so much a question of what one uses (because none of it is new) but rather where it gets placed and how it is managed to provide the best outcome.

The Queenslander comprises a fish tank, a sedimentation tank and clarifier, the growing systems, a sump tank and a trickling bio-filter.

While the Queenslander prototype was designed to grow the local species jade perch, it should prove similarly effective with any freshwater species.

The design of the Queenslander focuses on three areas…..component positioning, grow bed management and environmental control.  The first two strategies are about managing solids in the system and the third aspect acknowledges that virtually all freshwater species will grow best in a specific temperature range.

Over the next few days, I’ll feature each of the strategies in its own post.



  1. says

    I have a 10 gallon fish tank with a 5 gallon grow bed. For such a small system, do I still need a sediment tank w/ clarifier, bio filter and sump tank? What will happen if I continue to flood and drain four times a day without these components?

    • says

      Erich… would be a crowded little system if you jammed all of those components into it.

      For such a small system, I’d propose something like a couple of gold fish (which are pretty resilient) and some hardy indoor plants that don’t require a lot of light. Treat the system as you would a regular aquarium.

      For simplicity’s sake, I’d skip the flood and drain and just run it on continuous flow. Let me know if you require more details.

  2. John says

    Thanks for sharing your experience.
    I want to build a small flood and drain backyard system.
    I was really hoping that I could just pump the solid waste onto the top of the plant gravel. I thought it would be a great food for the plants, if it is processed by compost worms. Just wondering if it (solids) is really that bad, for the plants ?

  3. says

    John……you can build an aquaponics system which does what you describe. The secret to operating such a system is to keep it very lightly stocked. That way, the worms (and the beneficial bacteria) can keep things in balance.

    My concern around solids has less to do with the plants and more to do with the fish. (See 7 Good Reasons to Remove Solids)

    By the way, solids removal doesn’t have to be too onerous. You can catch the sedimentary solids with an orphan sock or a piece of filter foam at the point that the water enters the grow bed.

    If you keep the system lightly stocked and ensure that you have plenty of aeration, a little system like the one you’ve described will provide you with clean fresh vegetables…..and (eventually) a fish dinner or two.

    The key to successful aquaponics is regular water testing and being prepared to act when something is heading in the wrong direction.

    The Queenslander design concept is for the serious micro-farmer and will provide for much greater productivity (and safer operation) than a conventional flood and drain aquaponics system.

  4. John says

    Thanks again Gary for a very clear and helpful reply.
    Apologies, my first post was premature – I found your other pages, with their detailed reasoning later.
    I know little about aquaponics and have just started researching it.
    Just wondering, if one of the biggest problems caused by retained solids, is deoxygenation, wouldn’t fishpond aeration (with an air pump, for instance) solve that ?
    I mean, if you are concentrating on the fish culture, isn’t artificial aeration necessary anyway. ?
    (all commercial fish farms seem to have it)
    I read about your Queenslander system, but I don’t recall reading about whether you have an air pump, with it.

  5. says

    John……low dissolved oxygen levels is the single biggest cause of fish deaths in such systems…..but it’s not the only issue.

    Other potential problems include clogging of bio-filters (grow beds) and impairment of nitrification. Suspended solids may also function as a refuge for pathogens while they look for a live host – your fish.

    Fish gills can be damaged by solids while breathing and solids will, over time, build up in pipework and fittings and limit water flow.

    I regard supplementary aeration as being cheap insurance against low dissolved oxygen problems……so I run air pumps in all of my systems.


  1. […] would be very suitable. You'll see it described at length in a series of blog posts……starting here. Gary "All truth passes through three stages. First, it is ridiculed. Second, it is […]

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