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MT Mind

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MT Mind last won the day on November 26 2016

MT Mind had the most liked content!

About MT Mind

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    Advanced Member
  • Birthday 09/01/1982

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    West Texas, USA

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    Science, Sustainable Agriculture/Horticulture Especially iAVs and Bamboo, Mechatronics/Automation

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  1. I've thought about the same idea myself, especially when I overloaded my sand bed and the Nitrates continued to climb. I have to agree with Mark though, you're not likely to be improving on what you're already building. If you already had a DWC system, I would highly recommend adding a sand bed in line to capture solids. This would keep the DWC troughs cleaner and improve mineralisation, and you would have a place to put some tomatoes or something else that doesn't do as well in DWC. One problem with operation is the fact that DWC systems usually run continuous flow, but iAVs is an intermittent flood system. You can operate the DWC this way, but you'd be relying entirely on your bubblers for water movement around plant roots, unless you add a circulation pump for just the DWC troughs themselves, which is just one more thing to deal with. As far as nutrients being tied up in the sand, there's no reason why they would be held back once they are dissolved in the water. The sand will trap solids, but it won't retain dissolved ions. Any dissolved nutrients that aren't absorbed by plant roots in the sand when they are first liberated from solids will flow freely through the system until they are absorbed by the fish, bacteria, or plants. When you say, "Best of both worlds," what do you see as the best of DWC that you want to carry over to iAVs, and what is the best of iAVs that you want to carry over to DWC?
  2. Indeed, the water simply disappeared into the sand and never flowed laterally on the surface. I'm sure this is because the sand was too coarse, which prevented solids build-up on the surface. I wanted to see if I could "convince" the sand to flood by loading it with excessive solids, effectively reducing the drainage of the sand, and it appeared to work. It is possible that the system would have begun flooding on it's own eventually, as biofilm built up in the sand, but with air temps around 105F and water temps over 90F, the bacteria were working just about as fast as they could to break down the solids and clear the spaces between sand grains. I also wondered if the flooding would continue once it had started, with a reduced level of solids, so I cut back feeding once the beds had been flooding for about a week. The flooding ceased that day, and shortly thereafter I started pulling dead fish out of the system daily, until there were none left.
  3. I built a small iAVs system and sifted my own sand from a batch of "decomposed granite" by hand. I ended up with a mix that was larger than recommended, but still smaller than 3-4mm. I should have included smaller sand because the system drained to fast to work properly. Only by overloading the system with 50 goldfish being fed at 3%/day did it finally "flood" as intended, but I didn't have nearly enough plants to assimilate this much nutrient, so when the Nitrates got over 150 and stayed there, I started losing fish. Even then, I was using two pumps to get the necessary flow, which was way over the recommendation since they were cycling the 40-gallon fish tank twice in the 20 minute run time. Even a seemingly small difference in sand size can make a significant difference in operation. I highly recommend looking for sand that matches the C33 standard, if you can. I know you're not in the states, but here is a copy of an older version of the standard; it should give you something to work from. C-331.pdf Edit: I just noticed that I had missed the pictures of your sand and drain water. I'm concerned about how much your sand will settle over time, specifically regarding smaller particles washing into the lower part of the media and creating a muddy bottom that doesn't drain, but as you said before - it's hard to tell by eyeballing it. Best of luck!
  4. You are correct, and this is part of what makes the sand bed work so well. Instead of a pile of muck in the bottom of a gravel bed, most of the solids are captured in the upper part of the sand, and only water and dissolved nutrients pass through and back to the fish tank. IMO - Large aggregate flood and drain should not include solids in the grow bed; mineralization should be done before the water is sent to the plants, so the media remains open and oxygenated. Large aggregates are used in hydroponic flood and drain as a support for plant roots because the nutrient can flow into and through the media and flow right back out again, and they can work the same way in aquaponics if there are no solids. The filtration offered by gravel is mediocre at best, but solids will build up over time, as anyone using these systems can attest, making for an interesting mix of gravel and muck. Many people are growing in these gravel/muck buds, but conditions are hardly ideal for plant roots, and production suffers as a result. I've yet to see any pictures or videos of aquaponic flood and drain gravel systems providing growth that would rival what I've seen in simple organic soil gardening. I'm not saying those systems don't exist, but I haven't seen them. iAVs is basically an intermittent sand biofilter that we happen to be growing plants in, and the solids capture efficiency of sand is well documented. Very few, if any, of those solids will make it to the bottom of the sand bed. The surface are provided by sand for biological activity far exceeds gravel for the same volume, and the coarseness of the ideal sand provides for thorough oxygenation of the root zone as the water drains. This allows aerobic organisms to break down the solids in the root zone, instead of leaving it to the anaerobic organisms to rot the muck at the bottom of the bed. The sand provides an environment that's actually better for the plants than regular soil, and production reflects this.
  5. If they're using Sodium Chloride in their softener, I wouldn't add anything with Sodium to it; there will probably already be plenty of sodium ions in the water.
  6. In the U.S. the federal government establishes the regulations concerning what can be certified as organic, but the government doesn't do the actual certifying of an operation. The inspection and certification of a given operation is done by an independent organisation, which is authorized by the government to perform certifications. Different certifying organisations have different policies regarding what they will certify; many will not certify an aquaponic system of any design, saying that if it isn't in soil, it isn't organic. The regulations don't actually require soil for organic certification though, so there are certified organic aquaponic operations. All organic certifications still have to abide by the list of allowed materials for their operation. Some materials are strictly prohibited, like many synthetic pesticides and herbicides, but there are some materials that are allowed or disallowed according to how they are used. I believe many plastics are materials that are allowed as a container, but disallowed as a growing medium. This means that a DWC with styrofoam rafts can be certified, but the grow towers that Bright Agrotech uses cannot because they are stuffed full of shredded plastic refuse. The only major benefit of being "Certified Organic" in the US is the authorization to label your produce as "Organic" for market. Even if you grow organically, you can't market the produce as "Organic" without certification. As far as I know, there is not yet certification criteria for fish, so only the plant side of an Aquaponic system actually gets certified, more or less.
  7. I did, and it was on the shelf at home being used in the indoor aquarium for an undetermined amount of time. I picked up a new bottle shortly thereafter, but the system had cycled by then.
  8. I used API Quick Start for my patio iAVs, but I'm pretty sure it had expired.
  9. Yes, a pool skimmer will usually only handle a small percentage of the pool effluent. If the skimmer handles 10%, then the other drains will handle the other 90%. The Cornell dual drain design does not use a skimmer; it uses a side outlet and a bottom outlet. When the side outlet is handling 80-95% of the effluent flow, the bottom drain is handling 20-5% respectively. In order for the two drains to be handling less than 100% of the flow, there would have to be another drain added somewhere, which would be handling the remaining portion of the 100%. I think I'm getting an idea where the "clogged line" is.
  10. That's kind of how percentages work. With two drains, if the bottom drain is handling 10% of the effluent, then the other 90% of the effluent is going out the side drain.
  11. I'll second this. The merit of the Cornell drain is that the solids from the bottom drain can be filtered more efficiently because they've already been concentrated somewhat, if you mix that back together with the side outlet flow, you've defeated the purpose. My understanding is it would normally be set up something like this: Obviously, this is not to scale, just trying to show the logical flow sequence.
  12. I'm not looking for an argument either, but I am honestly interested in your input. The bulk of my personal experience has been with small plots of an acre or less. While I grew up on a large farm as a kid, We moved out of the business just as I would have started running machinery in the field. I am legitimately interested in your insights as a large scale operator, and if you would prefer to PM me, that would be fine. I apologize for being off topic; I apparently missed the point. I'm having a lot of difficulty interpreting your sentence structure, and I'm not sure what "in lieu with" actually means. Also, I'm not sure what water recapture technology is being used in any type of soil ag, unless we're talking container growing, which is usually done in a soil-less medium. I don't favor one system over another, but I think the merits of different systems have to be addressed in the context of how they are to be used. If you want to grow rutabagas over the winter, outdoor soil is probably going to be a better place for them than an iAVs greenhouse. I guess I'm really just thinking out loud here, instead of being helpful, but I'm still trying to figure out what box we're not thinking outside.
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