markor58

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About markor58

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    Ecuador

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    Tilapia aquaponics in the Ecuadoran Andes

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  1. Hi Phri Is this in case I want to breed my own? I might be doing that at some point, but right now with tilapia fingerlings selling for $55-$80 per thousand here, I'm thinking it's probably more efficient to just buy them, so long as they're good stock. There's a local-government-funded tilapia farm not too far from us where they do research and outreach and also sell fingerlings, so I'll be getting the fingerlings from them to start. Yes, I think I'm going to stock 50 fingerlings/m3, keep monitoring the water conditions, and cull them if conditions decline as they grow until I find the best density for my situation. Ok, I think I'll just get that make then - apparently if you hang them off a bungee cord they make less noise! My plan is to sell the fish for enough to cover the cost of feeding them, and maybe cover the electricity for the pumps/aeration as well if I'm lucky. Tilapia feed here sells for around $2/kg for the small fish and around $1/kg for the adults, and electricity is pretty cheap, so I don't think it'll be too hard to at least break even. The profits will supposedly come from whatever veg/fruit I grow in the system - right now I'm thinking tomatoes, tomatillo (possibly used to make our own salsa verde), or maybe uvilla, which you might know as Cape gooseberry. Absolutely! I'm going to start with either a 2m3 or 4m3 fish tank and grow the fish through from fingerlings to harvest in that, so I can work out best stocking density, best filtration area, and so on. Also whether it's worth doing at all! So for the time being I'm going to have rather a large greenhouse for rather a small tank - but if it doesn't work out I can always turn the GH into a very big sauna!
  2. My apologies, Mark - a case of 'assume makes an ass...' etc. Your clarification definitely - um, clarifies things. It also confirms (thank you) that I should be about right starting with 50 fish per m3, which will give me a biomass of 17.5kg/m3 at a harvest weight of 350g, 25kg at 500g. If that ends up being too high I can always start culling as you did and then reduce the density for the next cohort. Usually they sell tilapia fingerlings by the thousand here, but I'm sure I can find someone to sell me just a hundred. I think your posts are being vetted! BTW, thank you for the layout drawings - I know you can't eat appreciation, but I appreciate the time you must have put into it nonetheless.
  3. I think we're into suck-it-and-see territory here. I already have the insulation down (way too much probably, but there you go), and I need to put a solid slab floor on top of that anyway, so once that's done I'll put in a first tank and just see what water temps I get. I'm hoping I won't need more ventilation than a mesh-covered opening at ground level and just leaving the upper vent windows open as they already are, covering them with mesh to keep the bugs out rather than more polycarbonate. Only time will tell. Thanks for the link - that thing looks a beast - I counted 32 outlets on the manifold. It says 'Resun' on the label of the compressor shown in the picture, but the page title says it's an Elemental O2 model. Are they the same manufacturer? Anyway, looks a great buy. Absolutely - I have a tendency to fly off into dream land, but thankfully I also have a wife who brings me sharply back to earth! Yep - the fillets sold in the biggest supermarket chain here seem to come from 350g-size fish, and sell for around $6 a kilo - but if you go to a local street market they sell 1kg-size whole tilapia for $4. Basically I'll only know which route gives me better net returns when I get to that stage. I know you're supposed to have the whole marketing side sorted before you even start, but it isn't that easy here - different culture, etc. I'm English, but I like saying 'no worries' too! I also love all the Aussie slang connected to drunkenness - technicolor yawn, worshiping at the porcelain altar - love that stuff! How can an Australian be insulting when they call you a 'Pommie drongo.'? It just makes me smile.
  4. Thank you! It cost enough (mainly for the polycarbonate). I finally got around to measuring the temperatures in it this weekend - even with two end sections and all the little vent windows at the top completely open, daytime high was 40C (104F) and nighttime low (it was a chilly night for Cayambe) was 6C (43F). According to Ravnis the fish tank temps will be roughly halfway between these two extremes, meaning that just by adding a brick or concrete slab floor as a heat sink to provide a bit more warmth at night I should be able to get ideal temps in the tanks, I hope. I think it just boils down to it's better to give them more DO than less. I've now seen that there are chemical DO tests you can get which are far cheaper than the digital meters, which you still have to change membranes etc. on once a year, so I think I'll get some of those to make sure the DO is at the right levels. Regarding DO, I agree the simplest method seems to be airstones. I'll just get them from Amazon - you have to pay a $45 tax on small stuff shipped in to Ecuador, plus the shipping, but what the hell. I think I'm going to get the Elemental O2 Commercial Pump, 1744GPH, which costs around $70, and see how many tanks that will aerate to good levels. I tried a simple experiment with the centrifugal blowers which are widely available here, since I had one lying around, and quite apart from the problems attached to them being low-pressure devices, I'd forgotten how noisy they are! I agree it seems high - I just pulled that figure from Mark McMurtry's experiments back in the 80s, where he used 80 fish per 1m3 tank. Wilson Lennard recommends no more than 17kg/m3, which would be 34 fish at harvest weight of 500g, or maybe 50 if I harvest at 350g. Apparently the cost/benefit of feed input versus growth rate isn't worth it past 350g, after which tilapia growth slows considerably - do you have any thoughts on that? Best harvest weight? Anyway, I think I'll start with 50 fish per m3, and see how it goes as they grow. Thank you for your valuable insights, Phri, I really appreciate it.
  5. Thanks for this Ravnis! The study on DO and fish growth really hit home. Who wouldn't want to take an extra bit of trouble and spend an extra bit of money on oxygenating if it's going to DOUBLE fish growth? And reduce or even preferably avoid disease. I knew DO was important, but this really shows how important. Even if we're focusing on crop rather than fish production, faster fish growth means more poo, and more poo means more crops. To quote the study (which is quoting another study): "An experiment done on tilapia (Oreochromis niloticus) showed that FCR was inversely proportional to the dissolved oxygen level (1.45 at higher dissolved oxygen level and 6.75 at lower dissolved oxygen level) (Tsadik and Kutty 1987)." That's a HUGE difference. I'm amazed. According to the other study, one huge waterfall is very good at increasing DO, but having the water fall down lots of little steps instead of one big one actually encourages DEgassing. Interesting. I suppose the bigger the splash, the more contact with the air, hence more absorption - but why small splashes would encourage the opposite, I don't know. Also I'm not sure from the study if he's referring to just oxygen, since it's about getting nasty things like CO2 out of the water.
  6. Using Mark McMurtry's model, the stocking would be 80 fish per 1,000l (250 gallons) and a volume ratio of 1:2.2. Harvesting at 500g (1lb), that would give me a density at harvest size of 40kg (80lbs) per cubic meter of water (250 gallons), which seems quite high without all the bells and whistles of pure RAS - Wilson Lennard for example recommends a density of no more than about 17kg per cubic meter of water, although to be sure that is for the less efficient filtering of gravel grow-beds. In addition there is the problem of reduced oxygen at altitude - and according to the chart Ravnis kindly pointed me to, I have around 30% less available oxygen here than at sea level. So, the question is, can I safely rely on just the oxygenation from the water intermittently falling into the fish tanks for 15 minutes or half an hour every two hours during the day, given that I only have 70% of the oxygen available in the air that I would have at sea level? If I can, and if I only feed the fish twice a day, say at 10am and 12am, so the solids have time to settle and get pulled out by the last few drains to the grow beds, then, as you say, I can just run a separate aeration system during the night and not have to worry about suspended solids. My concern, though, is that intermittent cascade aeration won't be enough during the day with my reduced oxygen levels, along with the fact that research seems to indicate that it's better for fish growth to feed smaller amounts more often than larger amounts more infrequently. The feed manufacturers also recommend this. I know the focus is the plants, but I'd like to also farm the fish as efficiently as I can within those parameters. So, those are the questions I'm pondering right now. I see a very expensive DO meter and a lot of trial and error in my future.
  7. I've just noticed that Phri is following this thread, so hopefully he'll chip in on his own without me bugging him by PM - pretty please?
  8. I think I'm going to have to bite the bullet and fork out $200 or whatever it is for a DO meter, because according to that chart we're at the same level as Aspen with around 30% less oxygen than sea level, so DO could well be an issue. With the meter I can just try out the various methods for oxygenating while not breaking up the solids and see which works best. Or I could just PM Phri and see what he says!
  9. Definitely more like your early fall, except with the temp inside the greenhouse getting to well over 100F during the day. If I can keep the GH temp falling too much at night by using passive heating, then I think I should be ok for the tilapia without too much effort - ideal water temp around 80F. Right now I have plastic on the ground, then nearly a foot of recycled polystyrene tiles on top of that, which I think is probably way too much, but I can always take some out and use them for something else. I don't think many weeds are going to grow through that, but they can definitely seed in sand, so I think I will probably just lay bricks down on top of the insulation. I was just reading that the sun will only warm around four inches into a heat sink during the day, so I'm going to just lay one layer of brick and see what nighttime temps I get with that. If it's not enough, then I can do the whole pipe and blower thing and lay another couple of layers of brick, the top layer to be heated by the sun and the lower two by the hot-air pipe. Brick is definitely going to make leveling easier. Any thoughts about the up-welling water for oxygenation without breaking apart the poo idea? Have you tried that?
  10. Guilty as charged - there is indeed a slight bow in the roof. Basically I would either need more rigid roof beams or central supports to fix it. However, we never ever get snow here, and the rain runs off no problem, so I'm just leaving it as is. Next time I'll know better! I feel for you if your daytime temps get down to 20F! Here, it almost never gets down to freezing. Usually the lowest nighttime temperature will be around 40F. Remember, we're on the equator, so we basically have two seasons: slightly cooler and rainy, or slightly hotter and windy. Think permanent spring. Even at some 9,500ft above sea level, daytime temperatures right now are in the mid-70s and nighttime in the mid-40s. I'm going to measure all the temps this weekend. If the nighttime temps are low enough to warrant it then I'll definitely consider the heat sink and install that before putting the gravel and sand in. Actually, I'm now thinking of bricks - more stable and apparently better at absorbing the daytime heat, at least if they're denser than sand, which I think they are. Thanks for the great tip!
  11. This is a really nice idea - the Sunny John website doesn't seem to exist any more, but the whole heat sink idea is out there and seems simple enough, especially since I already have most of the work done for installing the pipework. According to the YMCA at Virginia Tech (makes me think of Roxy Music, shows my age) project, the amount it cools/heats does not seem that great, but I'll take the day/night temps in the GH this weekend and see how much I actually need. I also need to stick a tank of water in there and see how much the water temps vary day and night, which is the important thing since I'll probably only have fish in this GH. A very good point which I hadn't thought of. One of Gary's suggestions was a pump up-welling water from just below the surface, which wouldn't break up larger detritus since there's no splashing, but I don't know how effective it would be at oxygenating.
  12. The greenhouse is already pretty much built, just a few finishing touches needed. It has insulated polycarbonate walls and roof, insulation on the ground to prevent heat loss that way, and I'm going to put about a foot of sand/gravel on the floor for thermal mass. Remember we're up in the mountains, but also on the equator, so the temperature inside this GH gets up to well over 100F during the day. I'm hoping with all the thermal mass and insulation the temps won't drop too much at night. That remains to be seen. The crops greenhouse will be way cooler during the day, suitable for tomatoes, but I'll be running the water back to the fish house via black irrigation pipe. Since the water will only be exiting the fish house during the day, I figure I can just add more and more black pipe between the grow house and the fish house until the sun-heated water is coming back to the fish at the right temp. In terms of fish species, fingerlings are only readily available for two species here, tilapia and trout, and from what I've heard and read trout are way more trouble to raise. That's the theory anyway! The effect of altitude on oxygenation is a really good point, and it leans me even further towards 24/7 oxygenation. Maybe a small pump for each tank going up to a trickle tower using lava rock? Would that give more DO than a spray pipe? Here's some pics of the GH. The insulation is polystyrene tiles, some sort of packing material which I picked up from my local recycling place.
  13. Thanks for the input Ravnis. I'm trying to get my head around the cost-benefit of all these variables. Will the cost of running aeration 24/7 outweigh the benefit of presumably faster-growing healthier fish? Or will the benefit of being able to stock more fish via 24/7 aeration and therefore having more crop growing area outweigh the cost of the aeration? How much better do tilapia do with 24/7 aeration? Enough to make it worthwhile? This is important to me because where I am (up in the Andes) it's much more difficult/costly to get the conditions right for the fish than it is for the crops, so maximizing the fish efficiency is a biggie - the more fish I can have in the same-size (insulated) fish tank area, the more crops I can grow. I know I'm probably just going to have to experiment myself to get these answers, but if you can shine any light on any of this you would be doing me a big favor! I don't expect to get up to anything like the stocking levels of pure RAS, and nor do I want to - way too much technology involved - but I'm definitely leaning towards more fish is better than less.
  14. Hi Ravni - thanks for the welcome! There is an issue with acquiring an air stone/pump - I live in Ecuador and I've never seen any here other than tiny little aquarium models. I can always order them from Amazon and pay the rather high import duties we have here, but I'd rather use something that's readily available locally. Right now I'm tinkering with plans for an iAVs system, and the choices are between having one sump pumping to above ground tanks which drain via a SLO to the GBs and then back to the sump, or below-ground tanks as in the classic iAVs system with no sump, the water pumped out of the FTs to the GBs, and then draining back to the FTs. In either case the FTs will be around 2,000l and about 1.5m deep. Four tanks so I can raise the fish in cohorts and get a fairly consistent nutrient supply to the GBs. If I remember right, Mark McMurty found the best ratio of FT volume to GB volume to be 1:2.2, so that would give me 15 grow beds of 1mx2m at 30cm deep. Since I think it's probably better to have the FTs aerated 24/7, even with tilapia (I could be wrong), and the iAVs system only has intermittent pumping, I need some sort of separate set up for the aeration. When I was originally thinking about a continuous flow system, I was just going to include a trickle tower, but with iAVs that's not really an option, I don't think. Weren't you experimenting with iAVs?
  15. Thanks Gary, phri, all great suggestions. I guess the follow up question is which of all these varying methods is more efficient, in terms of energy use, ease of set up, and results. Anyone have any idea?