Aquaponic Gardening

A Community and Forum For Aquaponic Gardeners

>> We met at Don Stark's house, his greenhouse, actually. In all there were 7 returning members and 1 first-timer, though Gerry has her own new greenhouse.

>> For those of you who have not made it to Don's place, he has built a 20 by 14 semi-permanent hoop house out of PVC piping and a specialty fabric specific for his needs. He would be quick to tell you, with a smile, that there is a lot of duct tape and zip ties used in the construction as well. But this is his fourth year, and the hoop house is doing well, he has needed to re-do a number of growbeds as he learns more and more about the way things grow. [A side note: a group of greenhouse designers visited, looked at the duct tape, etc. stuck up their noses and commented that this was not a designed greenhouse, and have not returned. Don's point was that it was designed, but with cost in mind, not designer aesthetics.]

>> He has redone the Deep Water Culture (DWC) bed, when it began to leak. He has elected to line it with EPDM pond liner from Amazon, this go-around, as it was a good deal. This time he has insulated it from the ground with aluminum-backed Styrofoam sheets, he tells us that it does keep his water warmer than before when it was just gravel between the liner and the ground. The previous liner was 2 layer of 6 mil plastic sheeting which was anticipated to last 3 years, it lasted one; he is expecting much more from the EPDM.

>> He converted two flood and drain (Flood&Drain) beds to wicking beds by reducing the amount of gravel in the beds to about 2 inches, and setting up a stand pipe not a siphon, at 1 inch above the gravel. Then he filled the beds with  55 gallon plastic barrels cut into thirds (so one barrel yields three round sections about 12 or 14 inches high [did not measure]. He has bunched as many of these cylinders together in the beds, as he could, and then placed nursery pots in the big spaces left open.

>> He has filled the inside of these cylinders with coir [chopped coconut husks]. He has over-wintered some leeks, and some other vegetables, and is now ready to begin planting. [More about planting later, as there is a group project planned for next month.] He has experimented with placing some smaller nursery pots on top of these wicking beds, with the bottoms buried about an inch deep into the top of the barrel section filled with coir, and these also are getting enough water. So the wicking is possible for a significant distance, certainly more than 24 inches.

>> Don has also revised his Nutrient Film Technique [NFT] from gutters, open at the top, to big (6 inch) PVC pipe with holes cut in the top to hold 3 inch net pots. These pipes have been painted with a colorful spray paint to stop light getting into the PVC and allowing algae to grow in the system. When the algae die, they suck up all the oxygen from the water [to aid in the decomposition] allowing none for the plants. So, all the NFT pipes are painted, as are the water lines, and the connectors. He has some crayfish designed to live in that sort of environment to help clean out any algae that get to growing in the big pipes. The NFT beds, he feels, are best used for leafy plants like lettuce, other salad greens, and herbs. He does not use these for fruiting vegetables like tomatoes or peppers or high nutrient demand plants like brassicacea (cabbages, broccoli, etc.).

>> Don has retained one flood and drain system. It is in the upper one third of an IBC tank filled with a mixture of 1 inch crushed gravel, about 12 inches deep, topped with 2-3 inches of small pea-gravel to see if the pea gravel [rounded small stones about 3/8 inch size] can work to hold-up the plants. The pea gravel is easier on the hands to move aside as you plant and harvest. {My system is all 3/8 inch size crushed gravel. The difference is that pea gravel is smooth all over, while mine is still rough from the crushing. I think it has more surface area that way. [I may not be right!]}

>> What else is new? Well, Don has found that feeding sprouted fodder to his chickens as part of their diet is cheaper than supplementing with grain. And, it makes the grain's nutrients more available to the chickens or others (Don and his family) that eat it. The sprouting process opens up the grain and makes the carbohydrates much more available as well as allowing the proteins to become much more usable as well. The cost difference? 1-2 cents a day versus 7-10 cents a day.

>> So, what is he doing? He has purchased seven or so sprouting trays. He will put a small amount of feed, say 1/2 inch [I am uncertain of actual usage] then floods the tray with water, keeps it there for a period of time [unknown] to allow the grain to absorb water and swell. Then he drains the water out. A few days later, the grains will sprout, and at that point they can be fed to humans or livestock. Chickens, rabbits, sheep, goats, pigs, cattle, etc. all will eat the fodder, as it is now called for livestock, or sprouts if it is for humans.

>> So, a few cents of grains, processed to fodder, feeds more animals than the equivalent volume of grain would and is more nutritious (as the nutrition, already there, is more available) and not as expensive. Any food grain and some beans can be used, think mung beans.
>> If this were a retail operation, wheatgrass could be grown, or other seeds for sprouting, and marketed easily directly to consumers. A dimes worth of sprouting seeds becomes $3.95 of sprouts with water, time and plastic bins with home-printed labels.

>> Whew, that's a lot of information. But, wait! There's MORE!

>> Don, and Jessica (from Evergreen College in Olympia), are also concerned with energy and have independently developed air-lift pumps to cheaply push water from down-there to up-here. The cheapness comes from using low power air pumps to lift the water directly. The theory has been there for some time, and it is used commonly where there is sand or soil in the water to be lifted that destroys traditional pump mechanisms. As there are no mechanical parts to this pump, grit does not scrape into the mechanism, it just flows up with the water. Don demonstrated a small 1/2 inch pump and Jessica a larger 2 inch diameter pump. Both had achieved significant height of water pumped, both higher than expected.
>> It can't be that easy! Well, there are some trade-offs. (1.) The water flow is intermittent, burping out of the pipe at once then waiting for the next burp of water. Over time the volume can be significant, but the flow is always intermittent not continuous as a traditional pump does. (2.) The height of the water delivered is directly tied to the height of the water being pumped (by formula pump can deliver water to 1/2 of the height of the water it is submerged in. So, 6 feet of water would yield 9 feet of lift (measured from the bottom) or 3 feet above the height of the water. BUT, both Don and Jessica are getting higher lift than expected by this formula. [No explanation is offered.] Also, if the height of the water being pumped falls, say out of the bucket not being refilled, the height of the water to be delivered also falls proportionally.

>> However, if you pump up to a holding tank with the airlift, then the flow out of the holding tank can be continuous. Do bell siphons require continuous flow or can intermittent flow activate the siphon? Maybe, not much work yet demonstrated with air-lift directly to flood and drain, so to be determined.
>> Suppose you have an elevated tank being filled with water from an airlift pump. And suppose you have timer-assisted valves that open to draw from that elevated tank to the flood and drain growbeds.  How often should you open the valves to cycle the flood & drain beds? For the fish: cycle the all water in the tank every hour (aquarium literature). For the plants: four time a day (hydroponics literature). If I cycle my beds hourly, I get (45 x3 = 135) 135 gallons filtered an hour or 3240 gallons a day. (300 gallons of fish tank means 11 cycles per day, not 24.) But my fish filter is roughly the size of the fish tank, so I suspect more effective than a standard aquarium filter.

>> Could I go with less frequent cycles and still keep my fish OK? I don't know. Do you? Does it matter if you have a higher fish density per gallon than me? (I'm guessing that I have about 7-10 pounds of fish in my 300 gallon tank.) So my fish density is 0.0334 per gallon, today. By aquaponics literature one does not want more than 0.2 fish density per gallon (1 pound of fish per 5 gallons of water), so I have a ways to go before I threaten that level. And, I will be adding fish to the tank later this Spring. NOTE: I do not weigh my fish, I am going by a rough measure of a foot long tillapia will weight about one pound.
>> I'm guessing that if I increase my growbed capacity as my fish mature, that may also change the amount of filtration, and permit a higher density of fish in my tank.

>> March's meeting, will be the last Sunday in March the 31st at Evergreen College. Directions will be posted later, meeting to start at 2 PM (1400 for you active and retired military people).

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Replies to This Discussion

Air lifts can certainly trigger a bell siphon, once the siphon is triggered by water level in the bed, it will drain.  The air lift is also great for pulling solids out of the fish tank due to the "burping", or sudden rushes of water movement.  I watched this approach at work at the Aquaponics Association convention last September.  I still don't completely understand it, but it is very effective.


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