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  1. While fumigation is practiced in soil applications, the benefits of applying it to a biological system, as I previously stated (sterilization may not be a suitable option for a system that relies on bacterial activity), has no supporting evidence it would be effective or that it would not destroy the ecology the system depends on. When I talk about inexperience, again there is no evidence of people in this discussion with experience in the use of sand in a commercial context and even less with experience in commercial aquaponics. So, with limited factual information available, the discussion diminishes to circular conjecture. For example, in the last three posts I have the same thing in three different ways to no benefit to the discussion. With that I leave you to your ideas.
  2. Plenty of evidence sterilization needs to be undertaken between each crop. While sterilizing or managing a 10m2 garden will be easy at acre and above size, it wont be. There is special consideration to food pathogen not only plant and fish pathogen harbored by the media which is also the case for gravel and the other medias that can not be easily replaced. While I am neither way, I only caution its use at a large scale because there is no evidence that supports its use in a biological system. However, I can see this conversation is becoming circular which is common place where inexperience dominates the discussion.
  3. On my return to UAE last April, the system had been poorly managed for 3 weeks. The EC was above what I could read at 6.5... nothing of use will grow in that. The solution to nutrient reduction and reuse was to lift all of the rafts off 3600m2 and expose it to sunlight. Within 24 hours algae started and within 3 days the raft was covered in the thick blanket. See image below. Following that and the reduction of the EC, we recycled the algae through the trickle filter to capture and reuse it. However, the algae plays no significant role in the nutrient cycling on the farm. It was convenient to use the algae to capture the nutrient, then kill the algae and capture that for mineralization compared to dumping 1,000,000 liters of water and exchanging it. You guys are still over thinking the processes. Operationally at a large scale, sand would provide more headaches than benefits by the evidence provided so far.... and it would not have prevented this issue, nor would it have helped solve it.
  4. Which I have been agreeing with. Which also supports, my view that sand media has not been explored enough to say it is a viable option for commercialization in an aquaponic system. Hence people considering it should think twice before using it.
  5. Like I said I am not seeing any evidence that sand use in a commercial environment in aquaponics is workable. We considered it and set up a sand trail in two 30 x 8m greenhouses in the UAE, to investigate and perhaps find some evidence it can be used. But to date, I have not seen a convincing argument or evidence for its use. Perhaps in time evidence may be presented. Also I said, there have been plenty of trials and studies for the use of sand in hydroponics. There have been a few trials with aquaponics as well, not big but trails just the same.... However while they work well in the short term, they can be plagued with pathogen issues which require complete sterilization between crops, which is not a great option for a system that relies on biological activity for its success, such as aquaponics. Here is a bit of reading for you which goes to say there was quite a large amount of research into the use of sand media in aquaponics, so it has not been discounted, as I said it is not convincing enough, for me anyway. My preference is to test it first, which we are doing. I dont subscribe to Rackocy's work either for the very same reason, there is very little evidence it works in a commercial setting. At least not enough to convince me: McMurtry, M.R., et al. 1990. Sand culture of vegetables using recirculating aquacultural effluents. Applied Agricultural Research. Vol. 5, No. 4. (Fall). p. 280–284. McMurtry, Mark Richard. 1992. Integrated Aquaculture-Olericulture System as Influenced by Component Ratio. PhD. Dissertation, North Carolina State University. UMI, Ann Harbor, MI. 78 p. McMurtry, M.R., D.C. Sanders, and P.V. Nelson. 1993. Mineral nutrient concentration and uptake by tomato irrigated with recirculating aquaculture water as influenced by quantity of fish waste products supplied. Journal of Plant Nutrition. Vol. 16, No. 3. p. 407–409. McMurtry, M.R., et al. 1993. Yield of tomato irrigated with recirculating aquacultural water. Journal of Production Agriculture. Vol. 6, No. 3. (July-September). p. 428–432. McMurtry, M.R., D.C. Sanders, and R.G. Hodson. 1997. Effects of biofilter/culture tank volume ratios on productivity of a recirculating fish/ vegetable co-culture system. Journal of Applied Aquaculture. Vol. 7, No. 4. p. 33–51. McMurtry, M.R., D.C. Sanders, J.D. Cure, R.G. Hodson, B.C. Haning, and P.C.S. Amand. 1997. Efficiency of water use of an integrated fish/ vegetable co-culture system. Journal of the World Aquaculture Society. Vol. 28, No. 4. p. 420–428. Sanders, Doug, and Mark McMurtry. 1988. Fish increase greenhouse profits. American Vegetable Grower. February. p. 32–33.
  6. They are from Nate, because I could not be bothered looking them up. What makes them incorrect? Still makes not one bit of difference to the statement you made earlier about the ratios being somehow butchered as from mark to sperianeo to australia. The point is biofiltration of all the media is adequate at the 1:2 or even 1:1.
  7. Perhaps we get to see how well it goes in my next project?....
  8. Well it has been well and truly ascertained that ratios are not worth the ink they are written in. However, even taking the 1:2 ratio and let's take it from Marks work translate that to pea gravel and then onto clay media from a biological filter as you have determined is the basis for the argument. Sand 886m2/m3 Pea Gravel 280m2/m3 Gravel 69m2/m3 Required amount of biofiltration media needed for 70kg/m3 at 2% per day at 35% protein is 64m2 At the 1:2 ratio offered, all of the above media had adequate surface area from a biofilter point of view.... even at 1:1 the gravel will be borderline but it is a high feed rate... While I will admit growing plants in fish wastes is a new thing for me compared to my experience with fish, but I was growing commercial crops longer than any others mentioned....
  9. "With this size greenhouse anyone with good management skills has the potential to produce around 100,000 pounds of vegetables and 50,000 pounds of fish per year." I wonder why no one has done it?
  10. You can denitrify ammonia if the pH is low enough for the NH4 to donate its hydrogen.....
  11. I wonder if I can guess his new biofilter set up..... anaerobic and aerobic processes. Sounds great.
  12. While the wastewater info is relevant you need to keep in mind their objective it to remove it not use it..... so the processes are similar but we are targeting a different result.
  13. I think people need to read Marks papers a little more closely. The point I was trying to make with him, is there were no actual plant to plant comparisons for the sand, compared to gravel or raft so there is no evidence to suggest it is better or worse. Statements like "should be better" when comparisons are made have no place in a scientific paper, peer reviewed or otherwise. His work has not been discounted and it has been tested a multitude of times. I have seen it even in universities here in Australia and the results were less than impressive for systems that were older than 4 years. Even hydroponics has a go at sand. There is a large farm here in Australia that exclusively uses sand as a media. He was the receiver of lots of "err are you mad" feedback when he started. He managed to go well for a number of years, then needed to change the sand out.... no fish poo going in it and it still needed to be changed. He got more sand but somehow this one is magically eating his magnesium and giving him no end of trouble. Now adding solids to that may or may not produce better or worse results. At a commercial level it is a large risk because if the sand reacts with the nutrient, you will have a very large problem on your hands. Long story short.. I would think twice at least before using sand commercially because there is absolutely no evidence that supports its use.
  14. Yes I use two drum filters......