Backyard Aquaponics
A place to discuss aquaponics

We have a swimming pool in Tenessee(south/central) and wish to convert this 15 feet by 30 feet pool to an aquaponic garden afloat on pvc constructed rafts which would have a compost box atop the rafts. Lettuce, cabbage, swiss chard, etc.. are our test plants. We will terminate chlorine and install an air sparge for dissolved oxygen maintenance along with water hyacinths for purification. We also wish to tap the water reservoir for livestock ( chickens and a few cows ). Further we are installing a greenhouse over the pool and an adjacent bit of land to further our vegetable growing diversity. The goal is also to winter grow the land and floating raft vegatables with the greenhouse cover and the pool acting as a heat sink.

Our question among all suggestions offered is: What compost box bottom to use to allow the floating veggies in the compost box healthy passage into the water without releasing the compost to the water. Also what compost would do the job. These rafts would be stable enough to stand in for maintenance and we could move them in and out of direct sunlight. Fish could enter the system later. If successfull this should be year round production and variety if the additional greenhouse land can winter and yield crop. Any help in the box design and plant selection and how to manage the root system to recieve nutrients from compost and water is welcomed. We would of course begin the story here and add updates for all to read as this progresses. We are new to this and welcome any help for the initial attempt. Tazzer56

Welcome tazzer56, Sounds like you want to go big right off. I like that but you should read thru a lot of these threads to see what others are doing and get a thorough understanding because when you go big losses and dissapointments can be big also. Just a little pool experience of my own...dump your pool water. Algecide contains copper which will kill most fish. Lost all my catfish within a few weeks Bluegill didn't seem to hurt. Chlorene was long gone for months. Interesting idea about the floating compost, I hadn't seen it done yet but did read a few discussions about trying it. May be some anarobic problems without good airation. Sketch out your plans and post some photo's for advice.

Thanks for the response and I know too well about starting big. We really want to establish successfull wintering of crops over water and adjacent land under greenhouse cover. This presents the initial floating box and type of compost used as our difficult trial run component. If someone knows root growth of the lettuce type plants which we thought to try first, then compost selection, material for box bottom and construction might follow. Can plants such as these or others have a root system that can feed from the compost and grow for water take-up at the same time? Any help or resource to persue is appreciated and thanks for the response and heads-up. Tazzer56

Hey Tazzer! Welcome. Here is something to inspire you! Check out this vid and others by the same guy.

http://www.youtube.com/watch?v=c2z-IdnI ... annel_page

Cheers and all the best!

Just a few points you will want to research before trying to float a big box of compost.

******Compost gets really heavy when wet!!!!!!!!! Then plants will add weight. I don't know what sort of floats you intend to use that you think will support wet compost, plants, and a person standing on it without sinking the whole thing and still have space in the pool to move it around.

Compost also holds water really well. Containers full of compost suspended in water will likely stay too wet for many plants to be happy. Anaerobic problems. Compost may have it's place in limited quantities, perhaps beds that get fed by the pool water once a day or something but I probably would not try to float compost in a box in the pool.

For floating rafts you may be better off just putting net plant pots through a float like foam and putting some clay balls, gravel or some other media in the net pots. Granted, it wouldn't act as a floating platform that some one could stand on but I'm not sure how you are likely to manage that with a floating raft and still be able to have plants.

Now I am a little confused about the system you are trying to build. Sounds like you are not planning on fish, at least at first.
In which case it really isn't Aquaponics.
The main components of Aquaponics is a system that uses fish, plants, and bacteria to all support each other. The fish provide wastes that are the food for the bacteria which convert them to a useful for for the plants which remove the nutrients from the water, purifying for the fish. (components, 1 fish tank, 2 Bio-filter, 3 solids filter, 4 plant growing space)
-FYI flood and drain media filled grow beds can serve as 2, 3 and 4 all in one unit-

Skipping the fish and the bacteria, sounds like you are just planning on using pool water and compost for a growing system. This is a little more like hydroponics except that compost is really more like dirt so essentially the system you are talking about is more of an irrigation/temperature stabilizing system with a pool. While it is a rater interesting idea, I will warn you that much of the advice you will find here about it may pull you in different directions unless you are really interested in turning it into Aquaponics.

If you want aquaponics, then I would suggest that skipping the compost and using a more inert media for your grow beds would be a better idea. You can still make dirt/compost beds in the greenhouse that use water from the pool for overwintering your plants but re-circulating system water through compost is probably not a good idea for a fish system. Even if noting in the compost caused disease problems or built up to toxic level for the fish, it would tend to turn the water very dark and make it really difficult to see the fish. (I learned from experience by testing wood chips as a media for a grow bed, turned the water so dark that I could not see fish to even know if they were alive.)

You asked a couple times about what type of compost to use for this project. I'm thinking that you might not actually be meaning compost. (What I think of compost that means composted organic mater like manure and straw or leaves and kitchen scraps, etc.) If you are actually asking what sort of media would be good for growing plants in nutrient rich water, then that is a different question. Something like expanded clay balls, lava rock, or river rock are common Aquaponic media. Vermiculite and perlite have been tried but are more problematic and should be studied carefully before investing in them. Sand can even be used but it takes a long time to drain and can become anaerobic as well as being heavy.

Hopefully we can be helpful to you, please keep asking questions!!!!!!!

The fish are an ultimate goal and would be the final stage of this project. I can float some heavy stuff with six inch diameter PVC with end caps. The plant food ,be it compost or something else, is boxed and not in direct contact with the water while on the raft or float. The idea is to provide nutrient via the food source and water from the pool as a part of the root system grows to the water. A carefully selected mesh media as a bottom to the boxes could allow root passage to water and yet retain plant food for the shallow root system. This would allow water to stay potable for livestock and let me eat salad in february(witha the system greenhouse covered. I realize I am deep in experimental territory but trout and salad is a tasty combo. I watched the movie clip also and this whole concept I am presenting is open to wide variation and mods, but amodest attempt at the initial concept is what we are after initially. Please keep assisting as it inspires and educates. Diagrams and other specs will be posted for continued discussion and thanks, Jim(Tazzer56). Forwarding all to my Fam who will be joining the site soon.

I'm curious, have you ever seen some sort of very sturdy mesh that would allow roots to penetrate (and grow without being pinched off by the small mesh) yet would not allow particles from the compost or plant fertilizer to dissolve into the water and yet be sturdy enough to support wet compost and a person to stand on it?

Since you are planning on having fish eventually, you might be better off running a system more closely related to AP from the beginning so you won't have to worry too much about residues left from plant fertilizer killing your trout (they are rather sensitive to copper and zinc.)

What sort of filtration are you planning?

I did some experimentation with exactly the same thing you're attempting. I trialed three methods of DWC- 1) with plant roots immersed completely in the water; 2) with media partially immersed in the water but the roots of the plants higher up and watered through wicking; and 3) plants in pots setting on rafts, using two seperate types of media (perlite, potting soil) with a wicking material that was draped into the water for wicking but the plants themselves never touched the the pond's water surface. All three work well- some are better for some plants obviously but it is only one of two ways that I know of, where you can use soil-based media in an AP system without contaminating the fish water (the other is drain-to-waste and not water conservative). The biggest issues I had with the plants on top of the rafts were- the pot bases had to be flat for good contact with the wicking mat, you don't want uneven growth as the rafts will lift on one side, dry out and no longer distribute water to all areas and the rafts swamping with excess weight- I had large plants growing- tomatoes, mellons and cucumbers. I terminated my experiment for several reasons- lack of space for plants to grow on the rafts, no way of training the plants to alleviate the weight issue and I had a dog that would get in the water and distrupt the experiment. If you want to read my thread on the subject, it's in the member's system- Angie's First Prototype. Maybe it will give you some insight as to how you want to proceed.