Aquaponic Gardening

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It's finally almost time... I have some plumbing to do then I can get at least one table up and running with a temporary fish tank in place till I can build my pond. Plumbing is the easy part. I really want to buy some hydroton but at 7 each 50L bags for 1 table it's going to get real expensive real quick. I'm going to visit our local hydroponic store but we're probably looking at around $30 a bag. I have a "top soil" business right up the road that I can get pea gravel real cheap. I figured I'd ask the experts first. Your feedback could definitely save me big time!!! 

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There are master water test kits in aquarium stores that cost about $40.00.  You also want to get a General Hardness and Carbonate Hardness test kit.  Referred to as GH and KH.  In Portland there are no carbonates in my water I'm always adding Potassium Bicarbonate.  The best place I've found to get it other than brew shops is Nuts Online.

>.. That is a very nice system start. You are skilled in building, and I suspect, very skilled in plumbing. You won't need a huge pump to move water around. How do you plan to drain these growbeds? or are you going to dip out fish water and just add to the growbeds as they dry out. There are so many ways to do it.

>.. I'll be delighted to see more as you go along.

I wouldn't say I'm skilled really, but I am a marine pipefitter by trade and I have a degree in technical arts. I just like to create things. Growing things is the best though. Watching things change before your very eyes is the coolest ever! The picture with the 2 grow tables have missing slats to run my drains out the bottom. I plan to run 2 each bell siphons on each end of the tables for drainage. The plumbing will extend into the pond that I plan to install this summer.

To flood the tables I will be installing a halo PVC system that sits just inside the inner lip of the grow beds. I will be drilling holes in the PVC every 6 inches and placing them at a downward 45 degree angle completely around to enter water into the grow beds evenly. The pumps will be ran for 15 minutes a day, 4 times daily in an alternating pattern to ensure that I don’t drain the pond. Each bed contains approximately 75 gallons by volume, but most of that will be filled with medium for growing. Linda Logan and you gave me some pointers for my medium. I plan to drop approximately 1 to 2 inches of lava rock on the bottom, followed by limestone free pea gravel throughout the rest, except for the drainage areas. I will be separating the pea gravel with some plastic garden curbing (for visual appeal) and distributing coral in those areas as suggested by Linda Logan. I suppose I can do some estimation calculations to find out how much water will actually be taken from the pond but I’m not too stressed about it.

As previously stated, I plan to run a hot tub unit outside which will be used to stock fingerlings &/or trout and also act as a reserve for the pond. After cycling the system through a bed I will know the lower level of my pond. Once that has been established I can install a float valve in the pond that will draw water from the hot tub automatically. I plan to do the same thing to the hot tub as well with a line connected to my main water source.

I am quite aware that the system will need regular upkeep. And I want my system set on autopilot as much as possible. These two tables and pond are only a few things I have planned. After building the potting shed on the front of my greenhouse I plan to add solar panels on the roof to power the basics. Pumps draw approximately 15 watts. My solar panels collect 60 watts of energy. There are other items that will draw energy, such as my air pump, fans, synthetic growth lighting for off season growing, dehumidifier, etc. What energy I cannot collect I will use from a general power source and backed by a generator. Again, end goals are to have something that I would want to display in a magazine that is practically completely self sustaining.

I'll send you some picture of my system.  I suggest you do a bell syphon for drainage.  If the beds are level you'll only need to drop in at one point.  With the bell syphon you can control when the bed drains.  I also have overflow pipe in case something goes wrong.  I pump 6x/day using a timer set at alternate intervals on my system that has another type of drainage.  I also have another system that pumps continually using the bell syphon.  With a deep enough sump to feed back to FT you shouldn't have a problem.  The main thing I found was making the pump fit the flow need.  To fast and you run the risk of FT overflow and too slow you won't achieve the fill you need.  With a bell syphon no need for timer. So much info on bell syphon I'd go that route.  Then no worries about timing the pump.  Hope this makes sense.

I don't understand what you are saying.

 

I understand the science of a bell syphon. Once the table floods full the water beging flowing down the overflow (contained withing the bell). The bell creates a suction thus creating a pumping action. The table drains back down to the bottom (where the slits are at the bottom of the bell). The table stops draining when air is introduced back into the bell syphon which breaks the suction causing the pump action to occur.

 

I guess I just don't understand why I would want to run my pumps all the time if I could avoid wasting the electricity. Putting it on a timer allows for proper watering of the plants while eliminating excessive wear on your pump and reducing the use of electricity right?

I have both systems, one with three pumps on timers and one that runs all the time with a bell syphon.  Though I have had no trouble with the three on timers, some think this is harder on a pump to turn on and off.  As for the electrical expense I can't say right now.  Since bell syphons are so popular I think there are many on this site who can give a better answer.  I think Jim Fisk is someone I'd ask.

Good afternoon,

>.. In general, you are both right. Constant flood and drain IS more than the plants need; but intermittent turning on-off pumps hastens pump failure. A solution is to use as small a pump as you can to pump the water the needed height. For example, with the fish tank on the floor, you will have to pump higher to get the water into the growbeds, but if you lift the tank up sufficient to allow say 12 inches between the surface of the water and the base of the growbeds, you can use a much smaller pump. A smaller pump pumps less volume and slows the rate of the bell siphoning as lower volume means less often draining and maximizes the amount of air-time for the roots (desirable). Plants do well at 20 minute cycles (my greenhouse), but do as well with 4-6 hour cycles (literature on hydroponics). If you were to use a small fish-tank pump that could barely pump the 12-14 inches needed, I think one could get closer to what Jeremy wants. AND, smaller pumps use less electricity so fewer $$$.

>.. As a corollary fewer cycles means less filtration for the fish, so fewer fish is desirable over many fish for slow fill and drain operations by reducing the amount needed to be filtered.

>.. As a further corollary, small systems are much more susceptible to wild swings of test values as there is little volume overall to buffer changes. My two 250 gallons tanks will have much more buffer space than a 50 gallon tabletop aquarium, and are less dramatic in their changes. But a smaller tank is easier to do water changes when things get out of control, and dilution is the only course for safety of the fish.

>.. And yet another corollary, with less frequent water fall, air pumps may be necessary to keep the water sufficiently oxygenated. As most fish tanks have routinely pumped in air, this should be a minimal expense.

Keep the questions coming!

Boy, I'll tell you... I am so thankful I get to pick people's brains!!! You both have helped me so much!!! I'm already saving so much just by eliminating trial & error expences it's rediculous.

 

I had no idea that turning a pump on & off would increase wear on the pump. Now I see Linda's perspective. Keeping the pumps on regularly may increase electrical output, but if I have them running off a 60 watt solar pannel system with a back-up tirckle charger then it won't cost me really anything extra and I'll extend the life of my pumps.

 

Just to clarify: Using a smaller pump will slow the input flow rate into the table and it would take longer to fill completely. The bell syphon doesn't actually engage till there's an overflow from the overflow tube contained within the bell syphon. And the syphoning effect is due to suction within the bell which is caused by gravity pulling the water which creates a vacuum inside the bell. With gravitational accelleration being a constant 32 feet per second, how does getting a smaller pump or reducing the fluid rate input slow the rate of the fluid rate output when bell siphoning occurs?

 

Sorry for the technical question. I love physics.

>.. Never had much experience with physics after high school. But if the inflow is slow, the growbed fills slowly. the outflow is controlled by gravity, and should drain your small growbed in a minute or less. Even though the little pump is continuing to bring water to the growbed, it will NOT affect the drainage at all. You will want to have the growbed fill in less than six hours, but the drainage will probably take about one minute.

>.. When you site your drainage, allow about a one half inch of dry rock ABOVE the expected overflow point of the siphon. This will stop weeds from growing as well as moss. Just plant your seeds at the high water mark and when they sprout they'll come up to the light, and the roots will go down to the water.

 

Oh wow!!! Completely understood now. When you say slowly you REALLY mean slowly. I definitely have some calculations to do to determine what my water volume will be with medium in place to determine what the input flow rate needs to be to fill my table in 6 hours. Knowing this I will need to add a throttle valve to control the volume flow to my table. What is the optimal time to fill the bed?

>.. I would just start with a small aquarium pump that will just lift the height required. Use the surface of the water (in the aquarium) at the growbed filled-full level as your lifting surface level. If you set it up so one bed is almost full and the other is only beginning then your surface level would be higher. I don't think you want a flow restrictor on it until you have some idea about how fast the little pump can fill the growbeds.

>.. Have you calculated the volume of your growbeds? if so, gravel will fill from 40 to 60% of that volume. For practice in calculations, I would do 50%. There's lots of practical things that can make a difference. Say you get a pump that will lift one gallon a minute, that's 60 gallons an hour. Probably more than you want. But if you drop the level of the aquarium a bit you can slow the lift to maybe half or a quarter of that. A little more drop may make the pump, barely able to get water out. This is the practical part of plumbing for Aquaponics that they don't teach you in plumbing school, as you are usually working to design specs in the real world.

>.. As to timing of full and emptying cycles, don't be wedded to a number. Anything equal to 20 minutes or more is safe for fish and plants. If you can get longer cycles with your small growbeds then lots of others will want to know more, including me. Don't be trying for a set point yet; just make your system work. THEN fiddle with it. The simpler your actual plumbing, the easier it is to modify. I'm certain you will modify it several times before you are satisfied. We all sure have!

>.. Keep those questions coming!

I was thinking about getting a 1 gallon container, filling it full of wetted medium, then filling it full of water. To follow, extract all the water I can to determine a good estimate for the ratio per gallon. I know each bed is 6' (72") x 4' (48") x 6". This means one table is 20,736 cubic inches or just under 75 gallons. By multiplying the ratio determined by the 1 gallon container I can figure out the over all volume of water that will be drawn from my tank/pond. A volume flow rate can be determined by dividing the volume displaced by the time it takes to displace it. Provided that 6 hours is the optimal time then once I determine the volume displaced I will know my volume flow rate.

 

I totally get what you are saying about the height change manipulating the velocity. I can do this with my temporary tank initially. There is also a change in velocity when changing the overall distance that the fluid is required to travel (which should be taken into consideration). And, my pond will be stationary at ground level in the long run so adjusting the height WILL work initially. And by installing a flow restriction device, my biggest concern would be leaky fittings (and I'm a marine pipefitter by trade so I can solve that one very easily). Your thoughts?

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