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  • Gary's first Sandponics System

    I started on the construction of my first iAVs system in the latter half of June.

    Aside from being about five years overdue, it was inspired by some research conducted by the American University in Cairo. The researchers sought to compare iAVs with the deep water cycle (DWC) method. Their methodology was questionable which led me to think..."I can do better than that." And that's how this build commenced.

    I reported most of the build in the weekly 'Havemore Happenings'...so I moved the relevant reports here.

    23 June 2019

    This week, saw work begin on the sand biofilter for the iAVs…and the DWC grow tank.

    Since Havemore Farm is a constantly changing feast, my first task was to clear the site that I had allocated to the grow bed/tank. My NFT system – and a couple of shallow beds – were making temporary use of the space…so they needed to be moved.



    The NFT was easy. I simply created a new base for it – using cement blocks – and moved it across to its new temporary location.



    The shallow gravel beds required a lot more effort…including the removal of 600kg of gravel. Having seen almost as many incarnations as the Buddha, they are now stacked up – over behind the pond – awaiting their next deployment.



    Given that the new bed/tank will weigh around 1.4 and 1.0 metric tonnes respectively…and my particular circumstances are such that they need to be above-ground, they are of robust construction. I used cement blocks for the supports…and treated pine sleepers and formply…for the grow beds.

    I began to dig the holes for the sump tanks and it wasn’t long before Fate rolled up to the party…revealing some sewage plumbing right where I wanted to put the first sump tank…and forcing a change of direction for both me – and the sump tanks.

  • #2
    30 June 2019

    Frequent heavy rain stopped work on this system, this week…but sand beds were still the subject of discussion elsewhere in the world.

    Fresh on the heels of the iAVs/DWC comparison study conducted by Hisham El Essawy at the American University in Cairo (AUC), is another study that sought to compare lettuce yields between a DWC and with a “sand-bed system.” Like its predecessor, the latter study, by Lobna Salem (also from AUC), failed to optimise either of the units thus bringing the study outcomes into question.

    While I’m delighted that universities are starting to demonstrate an interest in iAVs (even when they are not aware of it), I regret that we were not associated with the researchers because these comparative studies would have been better served if they’d sought advice about what sand can do…particularly using the iAVs method. The rainy weather provided an opportunity to take a close look at both theses.

    The really interesting thing that has come out of the two AUC studies is the confirmation (yet again) of the versatility of iAVs. We’ve seen some outrageous deviations from the instructions and guidelines…and yet the iAVs (or other sand-bed aquaponics) still grows plants…and better than any other media bed that I’ve seen.

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    • #3
      7 July 2019

      I completed the sand bio-filter – and the DWC grow tank – this week.



      Both growbeds/tanks are made from treated pine sleepers – 2.4m x 1.2m x 400mm deep. These structures are supported on cement blocks. I used more treated pine sleepers to distribute the weight on the blocks. Each bed will weigh over a metric ton when filled with media and water.



      A sheet of 19mm formply completes the structural aspect of the growbeds. I should point out that I tend to over-engineer things…but this was also probably the most cost-effective way to accommodate my circumstances.

      My next task is to install the drains in the growbed and tank.

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      • #4
        14 July 2019

        While I completed the structural elements of the grow bed/tank last week, the ground under one of the cement block piers has settled to the point where the pier now a slight Leaning Tower of Pisa feel about it.



        It’s probably not a big deal – but these beds will weigh in excess of a metric ton once they’re filled – so I want to be absolutely certain that they’re safe to be around. The other issue is that every time I walk past them, I’ll know that one of the piers has a slant on it…and that will annoy the hell of out me. So, I’ll fix the problem before I line the beds and install the drains.

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        • #5
          21 July 2019

          This project was the big winner this week.

          I straightened up the leaning pier on the iAVs bed…



          …and drilled the holes for the flange fittings…before lining the beds with the local equivalent of Duraskrim.



          The flange fittings were bolted into place.



          The DWC tank drain was straightforward enough…that’s a simple standpipe arrangement. The iAVs drain was rather more complicated – in this particular application. It features a section of slotted agriculture drain pipe covered in a fine mesh sock to provide for effective drainage while ensuring that the sand stays in place.



          And then I waved my magic wand and 1.5 metric tons of sand moved itself into the iAVs bed. I secured the liner edges with some pine battens to finish off the sand biofilter and DWC grow tank.



          The sand that I obtained for this project is not ‘sand’ as we’d normally think of it…it’s glass sand.

          I used it because it satisfied the criteria for iAVs sand…it’s inert, free of silt and clay and it’s particle size range is such that it will drain very well. It was given to me so the only cost was for the transport from the mainland to our island…a mere $80.00. That it’s made from recycled bottles is a nice little sustainability bonus.

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          • #6
            28 July 2019

            I spent much of this past week thinking about this project and why, although the build is almost complete, nothing was happening.



            I’m so close that all I had to do is finish the sump tank installation and connect the pipework from the fish tanks and filtration modules to the sand biofilters and DWC grow tanks…but, with only a few hours of work to do, I felt incapable of making the final effort.



            And then I came to the realisation that the premise that underpins my comparison project is no less flawed than the research methodology that inspired it.

            The first research trial, conducted at the American University in Cairo (AUC) by Hisham El Essawy sought to establish which method (iAVs or DWC) was the better choice for Egypt – given its circumstances. While the methodology was flawed, this trial concluded that iAVs was the more effective growing method for Egypt.

            The second trial, conducted (also at AUC) by Lobna Salem, sought to establish whether deep water culture (DWC) or sand beds were the better way to grow lettuce. While the methodology for this trial was also suspect, it concluded that DWC was the better method for growing lettuce.

            Upon reflection, I concluded that my iAVs/DWC comparison was simply going to confirm the findings of the first trial. On the matter of the second trial, I came to the conclusion that knowing how to grow one type of food plant to the exclusion of all others, was actually of little interest to me.

            I also realised that by continuing with the comparison, I was going to lock myself into a regime of water testing, filter-cleaning and external nutrient mineralisation (or supplementation) that DWC requires but that iAVs does not.

            I was, in effect, going to devote a whole heap of time and effort to confirm what Mark McMurtry proved over 30 years ago…that, all things considered, iAVs is the most productive, resilient and sustainable way to grow plants using the metabolic wastes of fish.

            The other more disturbing realisation was that, even if I’d done all of the work that was necessary, it would actually have done little to change minds. I’ve observed throughout my 14 years of association with aquaponics that people act on what they believe rather than that which is verifiable fact.

            So, given all of that, I’m not proceeding with the comparison.

            Now that I’ve freed myself from that yoke, I plan to take the project in a different direction.

            I will now commission the iAVs as soon as I tidy up the few remaining build tasks and arrange for the purchase of some fish.

            One of the questions that I encounter, from time to time, is…”Could I connect a DWC tank to an iAVs?” I propose to answer that question as soon as I satisfy my initial curiosity about my new toy.

            After that, I’ll probably source some more sand and convert the DWC tank to another sand biofilter…and possibly even a second discrete iAVs with its own fish tank.

            There are so many questions that remain to be answered about the method but my first inclination is to determine whether there’s any discernible difference between glass sand and the quartz silica stuff.

            Comment


            • #7
              I was very disappointed to see that the comparison was halted. Not because I need any convincing one way or the other, but because I was looking forward to the candid comments.

              If you are into answering questions, I have been wondering if it would make sense to run a sand bed in the waste water stream from a RAS. Something in the line of backwashing the filters to a sump, then run a "fishless iAVS" to filter the water, and then re-use the treated water as either irrigation or makeup water back to the RAS. But now, having typed that all out, it sounds like a big hassle.

              Comment


              • #8
                Hi Nicol,

                I realised that iAVs and DWC were such different creatures that a straight-up comparison wasn't going to yield much that we didn't already know about either system.

                If there is to be any beneficial relationship between the two methods, it's likely to be that of a hybrid...where water that has passed through an iAVs then continues on through a DWC tank...before returning to the sump. The big question is about how that arrangement might impact the nutrient availability for either method.

                The DWC would benefit from the filtration efficacy of the arrangement...and probably even from the 'shared' microbiology (mineralisation) aspect of iAVs.

                The idea that greens grow better in DWC is sufficiently persistent to see some people want to combine the two methods...so, in some quarters, an iAVs might benefit from a salad bar attachment...allowing a wider variety of plants to be grown. The combination might well be attractive to backyard iAVs builders.

                If you are into answering questions, I have been wondering if it would make sense to run a sand bed in the waste water stream from a RAS. Something in the line of backwashing the filters to a sump, then run a "fishless iAVS" to filter the water, and then re-use the treated water as either irrigation or makeup water back to the RAS. But now, having typed that all out, it sounds like a big hassle.
                LOL, I think you've answered your own question. The charm of iAVs for me, as a systems freak, is that it lacks nothing and contains nothing that is not essential to its core purpose. It's the perfect system...which is to suggest that so long as you have the core elements in place, it is capable of an acceptable baseline of performance...just as it is.

                I came to this position after hundreds of hours of fruitless attempts to improve the method. Eventually, every idea for improvement took its last breath and I realised that the core system is perfect.

                Once you accept that...sand (of a particular type)...the furrows...intermittent irrigation events, etc...(the iAVs pillars)...are required, the potential for optimisation is huge. The core remains the same simple, easy to operate, cost-effective, sustainable perfect package that it always was.

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                • #9
                  wow Gary, i will look to your build for inspiration

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                  • #10
                    I came to this position after hundreds of hours of fruitless attempts to improve the method
                    Some things, like matches and buttons, cannot be improved. Rather than trying to improve iAVS, I am curious about what other applications can be, or have been, derived from it.

                    Comment


                    • #11
                      Originally posted by Nicol du Toit View Post

                      Some things, like matches and buttons, cannot be improved. Rather than trying to improve iAVS, I am curious about what other applications can be, or have been, derived from it.
                      I agree...the concept stands on its own...and, now that the iAVs ball is rolling, there will be all manner of adaptations as people scramble to own a piece of the iAVs puzzle. Ultimately, however, they have to demonstrate their efficacy against that of the original iAVs prescription...that's the baseline...and then there's everything that could be optimised through the use of modern cultivars and new culture methods.

                      There is already interest in coupling an iAVS to a DWC...and I share that interest because if the outcome of such a mating is that I can think of no better way to reconcile the production of fruiting plants and greens than to have it driven by an iAVs. Most of the benefits that accrue from the iAVs will transfer to the DWC...the water quality, the microbiology, the nutrient availability. Indeed, a DWC unit served by an iAVs is an improvement over the usual RAS model.

                      Comment


                      • #12
                        Originally posted by mikhail View Post
                        wow Gary, i will look to your build for inspiration
                        On the contrary, Mikhail...I've been inspired by your willingness to hang in there, mate. That's often a difficult thing to do when you...like me...often like to skip the instruction manual and dive right in. That's like learning to box by leading with your nose.

                        I'm delighted to be finally joining the brotherhood of iAVs operators.

                        Comment


                        • #13
                          Today, I filled the sump tank and began to recirculate water through the sand biofilter.

                          Comment


                          • #14
                            Hi Gary,

                            I'm enjoying reading your journey.

                            I'm interested in your thought process...(Sounds very similar to mine) You went gung ho into doing your own comparison between iAVs and DWC knowing that Mark did all the hard work 30 odd years ago, so you would know the result, then you changed your mind (I also do that and then ask myself the question why didn't I come to that conclusion before I did all this hard work?) But then interestingly, you decided to compare glass sand and silica sand as a growing medium. What made you think of that?
                            Is there some type of simple study or experiment that can take one grain of each and put under a microscope or some measuring device to determine which has the greater surface area? And I take it glass sand is oblique and sharp and has the same other characteristics of quartz silica sand?

                            Cheers.

                            Comment


                            • #15
                              Originally posted by bigdaddy View Post
                              Hi Gary,

                              I'm enjoying reading your journey.

                              I'm interested in your thought process...(Sounds very similar to mine) You went gung ho into doing your own comparison between iAVs and DWC knowing that Mark did all the hard work 30 odd years ago, so you would know the result, then you changed your mind (I also do that and then ask myself the question why didn't I come to that conclusion before I did all this hard work?) But then interestingly, you decided to compare glass sand and silica sand as a growing medium. What made you think of that?
                              Is there some type of simple study or experiment that can take one grain of each and put under a microscope or some measuring device to determine which has the greater surface area? And I take it glass sand is oblique and sharp and has the same other characteristics of quartz silica sand?

                              Cheers.
                              Hi BD...I'm pleased that my ramblings are finding favour with you.

                              It was actually my concerns about the research methodology that prompted my intention to do an iAVs/DWC comparison. Regardless of what prompted the change, I'm entirely comfortable with it since it will increase my understanding of the circumstances under which iAVs can be done.

                              The decision to use this sand was predicated on its availability. It was given to me by a friend so my only cost was that of transporting it from the mainland onto my island...$80.00 for enough to fill the 8' x 4' sand biofilter. That was a fraction of the cost of the next available option.

                              As I said earlier, it's more important at this stage to learn new things rather than confirm old things.

                              It's all coming together quite quickly now.

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