Consistent with the stated aims of this site, we’ve described iAVs – we’ve listed its benefits – and we’ve put all of the available documents into the Publications page.
What we’d like to do now is to start answering your questions – with a view to having you start up your own iAVs systems – and then we’d like to showcase your efforts.
So, if there’s something else you want to know – or if you have ideas or suggestions that you’d like to discuss – please leave your comments, questions or concerns.
-o0o-
Thanks for the feedback. I’ll try to design the my system to be able to run both ways (decoupled or not). That’ll give me some flexibility. In any case, it’ll take me a while to get the fish side of the system built and operational. In the mean time, I can support the grow beds up hydroponically.
Firstly, thanks to Dr M and Gary for all these information. I’m not a active blogger but I’ve read quite a bit on AQN and other blog sites. I appreciate the willingness to share. Also Gary, have a ton of respect for the way you responds to (sometimes nasty) posts from others.
I’m very interested in iAVS system. The articles here mentioned no special attempt to optimize iAVS in the prior tests done by Dr M. I figure since I am building a test system, might as well optimize it as much as possible. Seeking feedback on following ideas:
1. How should I effectively decoupled between fish and plant with iAVS? I know Gary have commented quite a bit on the decoupling/duel system benefits. I really like the way decouple system resolves various PH, temperature compromises. But given in iAVS, sand is serving as both the solids and bio-filter to return clear water to the tank, not sure how to do this? I have some ideas, but they are only partial solutions as best.
2. Instead of sand, would it be even better to have a mixture that is even closer to soil but still has very good drainage? I was thinking if the goal is to get the best env for microbes to thrive, why not just get as close to soil as possible, provided drainage and filtration is still ok? I was thinking bottom layer large river rocks, lay aluminum screen + nylon fabric, then mixture (1/3 sand, 1/3 compost or moss, and 1/3 soil), top dress with 1″ manure, add a bunch of worms. Drainage is my main concern … I tried this with a pot and water drains very well as soil is almost suspended by the screen off the bottom. Aside from higher build cost … do you think this can work even better?
3. Any experience with worms in sand or need a more soil like env? I feel sand might to cut into worms?
4. Looks like iAVS test done with tomatoes requires no further nutrient supplement. However, if I were to add other things, maybe we can achieve even better yield. What would be some of the regular supplement you have tried or may recommend? I am thinking worm/compost tea, calcium, and maybe seaweed type supplementation bi-weekly… thoughts?
I included some background and design goal info just as FYI. No need to read if not interested.
Background
– Main driver to save water (got drought), recycle nutrients, find high yield solution in smaller spaces.
– Focused more on plant production. Fish and shrimps are nice-to-haves.
– Home backyard food production for family or local charity donation. Not commercial. Hobbyist.
– Have experience with soil-based gardening and edible landscaping. Zero xxx-ponics experience.
Key Design Goals
– Low environment impact. Low water and energy use. Reduce use of commercial fish food, fertilizer if possible thru use of worms, BSFL, kitchen waste, yard waste, .. etc
– Looking for most efficient/high yield system
– Would like to involve some vermiculture
– Would like to have a dual loop, decoupled vegetable vs fish
– Low maintenance, as low as possible at least.
– Initial test system about ~1500 gal tank, 5 x 50sqft grow bed
– Ok with more upfront cost or effort to achieve above
Richard……Thank you for your kind words…..and for your interest in iAVs.
While I admire your desire to optimise iAVs, I suggest that you first attempt to match it. That will provide you with a contemporary baseline that is relevant to your circumstances.
1. iAVs is unlike any other aquaponics system….and it has more in common with soil gardening (using the fish to provide the organics)…..so we don’t really understand, at this stage, what benefits would accrue from decoupling. For example, there is no pH compromise required since an iAVS finds its own level and stabilised there. In the event of a disease or infestation in either the fish or the plants, you’d simply move the fish.
I’d be inclined to let your experience with your test system determine whether decoupling is actually necessary. iAVs does things that other aquaponics systems do not.
2. Sand is central to the efficacy of iAVs. It is not only an excellent filtration medium, it is also inert (both of which are important to the fish – relying on the interplay between air, water, organics (from the fish) and the soil microbes to feed the plants.
That’s not to say that what you propose wouldn’t work…..but it wouldn’t be iAVS…..and it seems like it would be much more complex to set up.
3. Worms will inhabit any environment that meets their needs. I’ve found them in trickling biofilters and media grow beds – and I can think if no reason why they wouldn’t inhabit loosely packed sand. Worms are not critical to the workings of iAVs.
4. The only nutrient shortfall that Mark experienced was with Boron in one particular tomato variety. He also grew peppers, beans and cucumbers with no problem. The only way to determine if you could grow more (faster/better) would be to trial it.
iAVs would satisfy all of the criteria that you listed. We know of no other more water-efficient system. It also ticks many other boxes including productivity, resilience and cost effectiveness.
Words of caution due to my just recent experience of buying 3 different manufacturer’s “washed builders sand”… “Washed builders sand” products are NOT all created equal… one particular product, after my inspection, did not even appeared to be “washed” at all even though was sold as such.
First buy just one bag and inspect it before purchasing a full pallet like I regrettably did.. Still I will put it to good use to replace my current gravel beds, but I would have preferred to have not made that mistake.
Just a heads up. 🙂
True, not all sources are alike – in fact none are – and not all quarry’s equally honest or competent. Also, I’ve been in quarry’s where every huge mound of sand there was of different ‘quality’. I’d ask if I can have a baggie’s worth (couple hand fulls) from each pile and then take it home and assess the ‘quality’ of each. There are several low-tech home diagnostic ‘tricks’ (too much to explain). Experience with sand and its ‘quirks’ helps. Then I pick from the pile with the least fines. A town near me has a concrete block/paver etc plant. They have over 20 ‘types’ of sand to choose/mix as needed. I always request samples first, assess, then choose. I’ve never purchased sand in bags. I’ve seen these priced and what they want for bags makes me shudder at the expense. Locally, a cubic yard is $30 (less with quantity). Sand is VERY heavy and can easily overload/damage your vehicle. Therefore its always preferable (and cheaper) to have it delivered by a ‘real truck particularly when buying more than a yard or so. I recently found an online source for aquaculture/aquarium filter sand of specific particle sizes. They wanted $13.5+ for 50 lb bags. That works out to $885/cu meter without freight charges. That’s insane. BTW, paid around $800 for 6 @ 8-10 yard loads, delivered, in 1985! Not anymore! ~ Mark
Did you come up with an efficient technique for pre-washing the sand before using? Or did you get the sand supplier to give a good wash before delivering the truckload?
“Mexican backhoe” haha never heard that one, but it fits in some cases.
Thanks very much for your help Mark and Gary.
No, I have not come up with one. But the sand and gravel industry obviously has. The sand I purchased was sold as “washed builder’s sand” which is typical for use with concrete and masonry. I have made attempts to wash fines out of sandy soil in the Sahel but can in no way claim that it was efficient or especially effective. Based on that experience, it is my position that it is more cost, water and time efficient to source a supply that may be further away but not in need of washing than it is to attempt to wash fines from a closer source. ? Never heard a shovel called “Mexican Backhoe”? Also known as “African Backhoe” and “Italian Spoon”. No disparagement implied.
Thanks very much for the response guys, very helpful. I’ve been going through the peer reviewed articles closely today and I have a couple more questions:
1) I see references to supplementation with calcium oxide, dolomitic lime, boric acid, and bone meal in two of the articles detailing the biofilter volume experiments. (These supplements were absent in the initial study.) In your experience has this mineral supplementation been necessary? (Obviously the need for pH modification will depend quite a bit on the water supply being used.) I imagine fish chow has changed in mineral composition since the 80s, so I wonder if you have encountered any deficiencies that required supplementation or foliar sprays?
2) Obviously the sand growing medium will transform into some sort of sandy loam (or loamy sand) after X number of cycles due to accumulation of fine organic matter. I imagine at some point drainage would be compromised and anaerobic zones would develop. Have you encountered this limit in your own experiments? How long have you been able to run your systems continuously? Do you add red wigglers to prolong media life?
At this limitation point I imagine the “spent” sand would still be an excellent plant growth medium, just not free draining enough to maintain aerobic conditions under such a heavy irrigation schedule – another advantage over gravel culture. I also imagine you could wash the sand at this point, but I don’t know how practical that would be.
Thanks again for taking the time to answer my questions; I’m looking forward to following the progress of your website.
1. Base additions were made to correct for the pH dive during the no crop interval (which was deliberate). Single Boron addition applied at 4-5th truss of tomato (first one I ‘think’) due to slight apical meristem whorl (initial symptomatology in certain tomato CVs)). No other supplementation. No other deficiency or toxicity symptoms observed or assayed. Some elements assimilated significantly above recommended sufficiently levels. Elemental composition of feed ration input was reported – as are the resultant (corresponding) leaf, whole plant and fruit tissue compositions. Don’t know by how much, if at all or how significantly, the currently sold rations may have been modified. Elemental analysis would be necessary to make such a comparison.
2. Approx. 2 years of usage with no negative effects on drainage observed. No evidence of anaerobic conditions. Eventually sand will certainly need to be ‘refurbished’ – aka washed. How long it would be before that’s advisable would be influenced by a dozen or so factors unique to each application, none of which I could potentially know in advance. One could have two supplies ‘worth’ of sand available and rotate as/when necessary. Yes, its work. I know ALL about moving sand with a ‘Mexican backhoe’ – by the multiple truckloads. IMO, sand’s benefits FAR out-weight any negatives. Obviously, I’m biased. Have not included worms but see no reason not and good reason to do so.
~ Mark
David….once the system was buffered for optimal fish/plant production (it’s something of a compromise in a closed loop system), no supplements were required for most crops. If anything, the latter-day approach to fish food formulation would probably mean that more nutrients were available for plants rather than less.
It should be said that we’re not claiming that all fish food will provide all nutrients for all plants. The particular fish food (an off-the-shelf proprietary product) that was used in the trials met the nutritional needs of the plants that were grown.
None of the research trials, nor the commercial trial, produced any concerns around the life of the sand media. Having said that, the various trials were limited to less than two years. Should it be deemed to be necessary, replacement of the affected section of the media (the surface) would no more difficult than other hydroponic media options (like rock wool bags/slabs).
If the worst that happened was that the “spent” sand was turned into quality gardening loam, that may open up a value-adding opportunity. Sandy loam is in high demand for things like turf farming and for use on golf courses…..or it could be used to moderate heavy clay soils elsewhere. The other possibility is that it could be washed (it may well have been washed prior to use in an iAVs system to rid it of similar organic matter or clay anyway) on site and re-used. The sand, once it has been washed, is inert and could be recycled indefinitely.
Composting worms would inhabit the sand if there was sufficient micro-organisms to sustain them – as they do with gravel media beds.
I was wondering if this system could be combined with a dutch bucket system filled with sand? The Fish Water would get pumped out to the buckets and then return via a drain to the fish tank. Perhaps some medium like stainless scrub buds could be added to the drains to help improve oxygenation of the return water supply? Just a thought. Nick
Nick….anything that respects the filtration/nitrification qualities of the sand is worth trying. It’s also important to maintain the 2:1 (or thereabouts) sand bed volume to fish tank volume ratio [ adding, volumetric ratio is dependent upon stock density and feed input rate ].
WOW! This is very interesting and exciting.
I have a few questions:
1) How is the fish tank aerated during the night in the third world manual pump module depicted in the paintings?
2) Is there a diagram of the cascade aeration anywhere?
3) Does the planting furrow protrude above the 30cm sand depth? If so, how much? Or is the planting furrow part of the 30 cm depth? If so, what is the depth of the base and the height of the furrow above?
4) Is there a screen or fabric at the base of the grow bed to keep the sand out of the fish tank?
5) I imagine this changes the stocking density to plant area ratios, any approximate numbers you can share?
Also, any clarification diagrams or photos of the hidden pipe drains, the weir, and connections for the drain apparatus would be much appreciated. (Also would love to hear from Gary about the central settling zone alternative.)
I have worked with aquaponics for about 5 years and have become somewhat disillusioned with the constant Fe/Ca/K additions, filter cleaning, and PITA factor of working with gravel. My personal system started with gravel tubs with bell siphons, and currently using passively aerated DWC of my own design (suspended corrugated roofing material instead of floating Styrofoam rafts.)
I am located in Mexico, where my wife and I work at a public university and also run a NGO specializing in sustainable agriculture projects in marginalized communities. We have successfully implemented a Rakocy-UVI style aquaponics module in a marginal urban community, but the system described here seems to have much broader applicability and the claims of mineral/pH self-sufficiency with only pellet food are very exciting.
I am very eager to build a demonstration module at the university and, if successful, start implementing this in communities ASAP. Mexico is in the midst of a food and water crisis that seems like it will only get worse, this type of innovation (or rediscovery…) could make a real difference.
Thank you very much for your efforts creating this site and (re)publishing this information.
David…..thanks for your interest. You’ve asked a number of questions – all of which we intend to answer – but it will take a little time. Some we’ll answer directly while others will be addressed in the form of short articles or multimedia presentations – and we also plan to introduce a Frequently Asked Questions section so that we cover off questions that (initially at least) we anticipate hearing over and over again.
plain text below = Gary. Italic below = Mark
1. There is no overnight aeration in this circumstance. The ‘low tech’ variant of iAVs assumes that the movement of water from the fish tank to the sand bed/biofilter happens manually. That’s not to suggest that aeration wouldn’t be desirable. One possible option would be to have some sort of simple wind device stir the water –
It typically wouldn’t be with Tilapia at low densities. Feed input would be restricted/withheld after mid-afternoon to reduce overnight BOD. OTOH, it would be possible (but likely not convenient) to move water over a cascade during the night hours without it actually passing thru the biofilter. I’m in no way suggesting this is the best aeration method and the absence of powered aeration options does reduce the stock capacity and yield (as represented in numbers used at Lo-tech examples). But it is doable and far better than nothing.
2. Not yet – and it does depend to some extent on the how the sand bed drain is set up. Google. And/or look at any mountain brook, waterfall. In general, the more the water flow can be agitated and broken up into droplets and the more times this can be accomplished during its fall, the more O2 will be gained. There’s a million possible ways to do this depending on what materials are at hand – and the terrain, layout configuration, scale etc.
3. The furrows can be accommodated inside a 12″ deep tray. The furrows need to big enough to support the plants being grown and to hold their shape as they are flooded. The solid wastes and algae may partially clog the sand surface in the early stages of plant growth. The “islands” formed by the furrows facilitate gaseous exchange and ensure that the plants receive water while avoiding the crowns of the plants being exposed to rot.
The 30 cm is an approx. min. depth at the shallow end of a bed. The longer the bed the deeper it is at the drain end since the top surface is level and the bottom sloped down toward the return outlet. The furrows I made were formed ‘into’ – below the original surface, ridges were not built up above it. Incorporate a few inches of ‘freeboard’ above the sand surface into the bed design. For picture of furrow, see R411 Folio Reprints in our Publication section.
4 Nylon or fibreglass insect mesh is one option. A bank of small gravel around/across the drain outlet will also retard movement of the sand through the drain. Yes and no. There are so many options. Drainage velocities aren’t sufficient to transport sand grains to any significant degree – if at all. Every ‘system’ I’ve created was different, ranging from no ‘screening’ at all, to a 1/4” mesh and pea gravel at the outlet. Never had a problem with sand getting into the tank or a sump. Not a concern IMO. As time permits, we’ll get to describing ‘grow bed’ construction in further detail.
5. I’m assuming that you’re referring to the hand-operated version of iAVs…..
Not sure what “this” is/means – but, Yes, stock density and feed rate are both proportional to filter capacity and plant growth (numbers, light, temp, stage, rate, spp. etc). This is a complex topic not lending itself to a one size fits all answer in a comment response.
6. Also, any clarification diagrams or photos of the hidden pipe drains, the weir, and connections for the drain apparatus would be much appreciated.
No “hidden” pieces parts anywhere. However, in large biofilters – such as at commercial scales – drainage pipe/tiles with water permeable fabric cover is advisable – but not necessary at small scales.
We’re currently working on some diagrams that will help you to better understand iAVs.
Gary /Mark
I am interested in trying this idea in a backyard garden or perhaps greenhouse application. I have a small indoor RAS at the moment and am considering adding a small grow bed with artificial lighting to it and was wondering if this sand bed would work in that situation. Also, I wasn’t able to view the first 2 publications for some reason so forgive me itf this was answered, but how is the water distributed to the bed? Does each furrow have a water input from the tank or is there just 1 for the whole bed. And how is the flood/drain cycle controlled? It seemed to me with the weir set up that the water would possibly run back to the tank without thoroughly watering the bed. Thanks for the information. A very interesting concept.
Thank you for your interest and feedback.
RE: viewing documents – You may need to update your version of Adobe Acrobat and/or Viewer but we’ll notify the tech’s to see if there is a problem on our end.
RE: Water distribution : by ANY means available, most likely an electrical pump in a 1st world context. Submerged centrifugal low-head pumps work well (there’s no substitute for quality). Sizing the pump displacement capacity depends on your tank volume and effective head (lift).
Level the top of bed surface, bottom of filter sloped toward return outlet. Add furrows around the perimeter and connected to furrows between each crop row (furrow bottoms also level, let the water flow ‘show’ you). Apply water at any point and it will ‘seek its own level’ and evenly distribute along all connected furrows.
An example bed furrow is seen in the first image of the second publication from the top (which you’re presently having difficulty accessing). This example shows a PVC manifold (pipe with multiple smaller holes facing down) to reduce the water velocity and thereby prevent scouring (erosion) of the sand – but a few ‘splash rocks’ will also work for this purpose.
Irrigation is scheduled with a timer (if using an electrical pump). Depending on precise drainage characteristic of your media (percolation rate, hydraulic conductivity), a general ‘rule of thumb’ is to start-off by moving approximately 1/4 of the grow-out tank volume in 15 to 20 min per event. Allow biofilter to drain completely and leave drained for 1.5 to 2 hours. Drainage ‘should’ be observable within 5 to 10 min from initiation of the pump cycle. Repeat this cycle approx. every 2 hours during daylight hours (begin at dawn).
Depending on your latitude and season, this should allow approximately 7 to 9 cycles per day and will turn-over (filter) the entire grow-out tank volume twice a day. Tank should be configured to allow consolidation, concentration, settling of the solids where the pump can easily remove it during each event. Because the pumping occurs during the daytime, this is well-suited for solar-PV pumping (in a sunny climate). As with virtually anything else that’s electrical or mechanical, having back-up(s) is strongly recommended. [ If your RAS tanks don’t include a central settling zone, Gary might chime in with another alternative he’s considering using.]
Fine tuning the irrigation volume and on/off cycle times will depend on the drainage characteristic of your particular media – not all (or any) sand is ‘equal’. We intend to furnish more details on all aspects and componets as time permits. This site is just getting set-up. Check back frequently for updates.
RE: retaining weir – that example was for Lo-tech application such as in the African Sahel. The container you build/selected for the biofilter need be lined with EPDM or another food-safe impermeable membrane/barrier, with an single outlet (crack, gap, slot) for return drainage at the bottom of the lowest end/side of your filter (bottom of filter bed sloped to drain/return to the fish tank. Many other configuration/layout options are possible. The ‘Lo-tech’ illustration (and others) are suggestive of near ‘infinite’ possibilities.
Depending on your fish species, stocking density and the feed input rate one can also configure multiple biofilters per tank. Each biofilter would have the same general irrigation schedule as above but they can be staggered in time allowing for greater cumulative turn-over (exchange rate) – even constant flow out of the grow-out tank volume is possible if desired and the volume of ‘wastes’ is sufficient for the number/type of plants grown and their growth stage.
RE: concept – is also proven – in the true definition of that term.
PS: If you’re at all like me, then when you’re ‘getting busy’ at leveling the sand and forming the furrows, it will take you back to the ‘good ol’days’ of playing in a sand box and/or building sand castles at the beach when you were a child. Age regression can be most therapeutic, if you allow it to be.
~ Mark