Recirculating Hydroponic System with No Water Change

by Kaushik Patel
(Montreal, Canada)

I am going to try DWC for the first time, but with Zilli Tilapia's and bioballs, which is use to convert ammonia to nitrates. Basically, it is an aquaponic system which recirculates the water. Now, if I add nutrients to my system, will I have to change the water every so often? And /or will my Tilapias provide enough nutrients to my system (which I don't think will happen). Also, I will be having different stages at one time....will having a high ppm hurt my early stage roots? Or do I have to have different systems for different stages? Thank you Guru for lots of info you provide!

Answer: Kaushik- this type of recirculating hydroponic system, using aquaponics to fish-farm, is a little outside my expertise. Anyone who has ever managed an aquarium can tell you that high nitrate levels will begin to kill your fish. I have talked with at least two other visitors who are trying aquaponics, and this seems to be the biggest sticking point in the whole operation (balancing the Nitrate requirements of the crop with the Nitrate requirements of your fish).

Most crops you would like to grow require Nitrate levels that are too high to be healthy for your fish. The fish, on the other hand, would prefer very low levels of Nitrates, but will tolerate medium-low levels without too much of a problem. If you are serious about bringing this type of recirculating system into perpetual balance and harvest, this leaves you with a handful of crop choices. The most common ones I have seen are micro-greens, lettuce, spinach, and herbs that produce vegetatively....which include rosemary, basil, oregano, mint, sage, thyme, and others.

Running a small worm farm is one option I have discussed with another visitor. Tea made worm castings can add Nitrogen, Phosphorus, and Potassium to the water in your system, but does not seem to bother the fish as much as other Nitrate sources. Also, the redworms can be used as a supplemental food source for the fish.

Having a high ppm will hurt your fish more than it will hurt your younger plants. Be sure to do a little more research into what levels of Nitrate (and other plant nutrients) your fish will tolerate before deciding to add any additional fertilizer to this type of system. In a recirculating hydroponic system, growing the crops I have mentioned above, a balance can be achieved. Certain Nitrate levels can be maintained that do not affect the fish negatively, but which allow for several crops at different stages to be grown and harvested simultaneously.

One of my other visitors was actually using 1 1/2 inch thick styrofoam, similar to the lids made for this system in order to float each different crop as he added them to his system. He was also farming Tilapia, using bioballs, and was growing many different lettuce and micro-green varieties in a perpetual, recirculating fashion without any water changes. I hope this gives you some good ideas Kaushik. I would love to hear how it turns out....and Happy Growing!

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Aug 02, 2012
Aquaponics, new, exciting, tough NEW
by: Anonymous

Hello, I am digging the blog. I am totally interested in aquaponics, and I have watched a bunch of great videos about it on youtube by Murray Hallam. I imagine that the pH of an aquaponics system would be nightmarish to manage. Murray says that a 250 gallon reservoir is the minimum size if you don't want to be constantly adjusting the pH. I feel like aquaponics is a great idea, and is a really cool sustainable way to grow your own fish, vegetables, and whatever else you want to do hydroponically. I feel that the one downfall is that you can't push your plants with nutrients without hurting the fish. Has anyone ever seen an aquaponics setup with large plants with bulging flowers?
I love the idea of using worms to make a tea, and also to feed your fish! You could litterally turn your old food scraps into worms, and then into fish and vegetables. INCREDIBLE! I know that there are a lot of advances in growroom technology as far as controllers go. Perhaps the use of a grobot or HF's new autopilot can help maintain smaller more personal sized systems.

Jul 18, 2010
by: Kevin

I was deeply interested in this, too, and did some major research into this. There also recently was a documentary on this very subject. The farmer (of both fish and crop) added no extra plant nutrients at all. It was far too costly to increase the nutes, kill some fish in the process, when he found that for his set-up it was more-or-less in balance anyway. I have used seaweed and fish emulsion to great effect, and recently I have also been trying diluted fresh human urine, which works surprisingly well (but a bit smelly for a day!)

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(10 week update below)

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Hi everyone, Jason from Jason's Indoor Guide here. When I got started with hydroponic gardening more than 24 years ago, my first garden used rockwool cubes and B.C. Nutrients....and I remember thinking to myself yeah, sure, there may be a lot of advantages to gardening with hydroponics, for example there are very few pest problems, therefore very little pest control, no weeding, no plowing or tilling the soil, no soil testing or having to add things into the garden soil, no watering the garden....but for someone who just wants to grow their own vegetables and have more control over their food supply and the quality of the food that they eat, the cost of constantly having to buy grow media and hydroponic nutrients makes this an expensive hobby for most people...

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I suppose when you take into consideration how much money you save NOT having to buy food at the grocery store, it is surely cheaper to grow your own food hydroponically even with the cost of high quality nutrients. Nevertheless, I didn't have a whole lot of money to work with and I needed to make my efforts as affordable and effective as possible....and in the last 24 years I HAVE learned a thing or two!

As you browse through Jason's Indoor Guide, you will notice all of the systems that I use personally are homemade systems. As I got 3 or 4 years of experience under my belt, I quickly adopted a preference to standing water systems and systems that use expanded clay pellets or lava rock, because the media is re-usable and it eliminates a huge operating expense. So once a hydroponic system is built, garden maintenance is minimal- check and adjust the nutrient solution daily, and to change it completely every 2 weeks....and the biggest operating cost is the hydroponic nutrients. (and the electric bill, lol)...

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And, regarding the cost of the nutrients....I experimented for about 3 years with making different compost teas and nutrient teas, but there is still a lot of expense $$$ associated with making high quality nutrient kelp meal, liquid seaweed, rock dust, bat guano, un-Sulfured molasses, worm castings. You can eliminate a lot of this expense by becoming an expert at making high-quality colloidal humus compost, and use your properly made compost as the basis of your hydroponic nutrient solution.

Unfortunately, I have been gardening for over 24 years and I have only just recently mastered this difficult skill....and even then, only because I happened to find a very easy to follow, high quality technique and decided to follow the instructions to the letter. I produced more high quality compost in just one week than I was able to use in a whole year! If you can master the technique, I highly recommend it. It is one of the top 3 things you can do to increase the productivity of your food production efforts, while at the same time decreasing the amount of effort required to grow all of your own food, and decreasing the total cost of operating your food production system.

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This solution is aquaponics. If you are serious about producing all of your own food and being self-sufficient, this is the ultimate solution for reducing expenses (as much as possible), reducing the total amount of work required, and maximizing the productivity of your gardening efforts. I have been gardening for over 24 years, and it is the perfect food production solution in my opinion.

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The Same System/ 10 Weeks Later!

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