Aquaponic Gardening

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I am an experienced gardener that is wanting explore the idea of aquaponics. I would greatly appreciate any imput/help on my questions.

To start off we have a 4000 gallon 3 1/2 year old pond with aquatic plants and about a dozen koi rangeing from 1 to 3.5 lbs. The pond has a 3 stage filter system containing two 55 gallon tubs followed by a 250 gallon rubbermaid tub filled with cattails and other plants. As of today the levels are as folows PH 6.8 Ammonia < .25 ppm, NO2 0 ppm, NO3 about 5 ppm.

The crops of choice would be tomato, cucumbers, squash, lettuce and others may follow.

The greenhouse will be located next to the pond. The water will be pumped from the pond threw the bottom of a raised IBC tote. This tote will be a sand upflow filter. The water will then overflow into a second raised tote that will act as a reservoir. The water will gravity feed into the Tomato NFT system from this resevoir. Now the pump will remain on and as to make sure that the second tote does not overflow. I will have a 3" pipe connected towards the top of the reservoir to allow for adaquate drainage. This pipe will lead back into the pond.

Now I know that tomato roots get quite large and have read about them clogging up 4" PVC easily. To counter this problem I was planning on getting 8" drainage pipe and cutting it in half as to make an open gully. For the top of the gullies was thinking about using plastic roof sheeting (^---^---^---^) that is cut into 8 inch strips. There would be 4-5" holes that I could cut into the center of the roof sheets every 2'. These holes would contain baskets filled with hydroton to support the tom roots. My major question is that... the 25 sq inches that the gully with the lid creates, is that enough room for the larger tomato roots?

Once the water passes threw the trough past the tom's it then connects back with the 3" drain pipe back to the pond. Now instead of having the water constantly go threw the gullies I was thinking of putting it on a timer that creates more of a "Flood and Drain" effect. I feel this will insure an adequate amount of oxygen to the roots and create sort of an ebb and flow cycle. Any input as to how long of flood time for the roots as compared with the drain/drying time? Also if the roots sit about half way into the trough how high should the water level be in the gully? IE touching the bottom of the baskets or not?

I am new to this whole idea and would greatly appreciate any imput/ comments on this. I am still in the design part of the garden but would love to move forward asap. I know this is a lengthy way of presenting my questions, but was trying to paint the best picture i could.

THANK YOU for your time!!

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For NFT, people have found that the "flood and drain" effect doesnt' really help the roots get oxygen as much as you might expect.  You will be far better off adding lots of aeration to that second tank in the greenhouse and making sure your troughs are not too long and running the constant flow like normal for NFT.  That trough might be big enough for tomato roots but they will also probably still manage to get big enough to clog the trough, it will depend on how big you let the plants get and how long you leave them to grow before changing them out (I've seen tomato plants that managed to fill a 100 gallon stock tank with roots and then go on to start clogging the drain.)

Do you do water changes on your pond?  You may find that if you don't have to do water changes and your pond is already well balanced with the pond plants, you will need to feed the fish more to have enough nutrients to make your greenhouse veggies happy.

Thank you TC,

As for water changes, yes we do them as needed about 10% at a time usually once every week or so but only in the spring,summer,fall. We are not feeding the fish now as we are not supossed to. which is why the ammonia/ N02 NO3 levels are so low. or at least that is my guess. As for the Tom's I was planning on letting them go full term. Should i replace them after a certain point or let them grow till they stop producing? So your saying that in a constant flow NFT system the roots should get plenty of oxygen? We were planning on putting a verticle arriation  tube from the second tank to the beginning of the troughs. this tube will constist of a bunch of rigid plasctic pieces as to create as much arriation as possible.

Once again thanks for your time.

another question, Can you feed your fish too much to where it endangers them? other than ammonia being too high.

The aeration tower before the NFT tubes sounds like a pretty good idea.

As for how long to leave the toms go, I'm no expert but I expect you will leave them go until the production drops or till they annoy you too much with clogging the troughs.

I don't know if the fish will eat themselves to death like some dogs might but if you are over feeding the fish and uneaten feed is building up anywhere, THAT can endanger your fish.  Over feeding (and leaving the excess feed to pollute the water) is the single leading cause I know of for fish kills.  And rotting food in the tank causes more problems than just the ammonia spike.  It can be a breeding ground for fish disease and if it becomes anaerobic anywhere it can give off hydrogen sulfide which is really toxic to fish.

That said, yes you are right, this time of year you would not be feeding and the nutrient levels will drop, that is normal.  But as you get into warmer weather and start feeding the fish again, hopefully your aquaponics will balance out any need for water changes and all you will be doing is topping up the water instead of changing it out.

Thank you very much, i will take all this into consideration. If i have any further questions ill be sure to ask.

I plan to start in early march. Building the system before of course.

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