Backyard Aquaponics
A place to discuss aquaponics

Rupe, and this is where I'd like my system to be different. My objective is to make it full recirculating with the normal (very small) water changes that we have become used to in AP.

We are also in the process of buying a roto-moulding machine to turn out GB's similar to Joels, the only difference is that our's could be stacked 2-high. The single GB's would be gravel with watercress etc. in gravel and flood and drain and the "double-decker" GB's having "soil-compost" mix in the top bed with water wicked up from the lower GB which would essentially just be a water reservoir. Water will slowly flow into and overflow from this lower container. The plants in this system would benefit from the nutrients in the "soil compost" mix as well as the nutrient-rich water.

I have no doubt that a LOT of research is still needed but I have just taken on a Masters Student from Stellenbosch University who has all the time in the world and will be writing a thesis on some of the crazy things that I am trying and will be invaluable for research purposes.

Interesting concept Synapto.. and one probably worthy of a thesis...

But I'm a little confused as to just what the premise or outcomes of the study might be?

Is it intended to demonstrate increased yield/area in comparison to an aquaponics system of the same area??

Is it intended to demonstrate any additional nutritional value of the yield??

Is it intended to demonstrate any improved growth yield of fish stock, or shortened grow out times??

Is it intended to demonstrate increased profitability of such a system, either through improved yield/area or by lower capital cost in infrastructure???

In short, what exactly is it that you're trying to acheive....

At first glance, it would seem that the single watercress growbeds, while providing bio-filtration... are essentially non-productive and neglible revenue raisers

Similarly, the bottom growbed of the "double=decker" growbeds are only water reservoirs... thus non-productive and nil revenue generators...

Leaving only the third top growbeds with the soil/compost media as productive revenue generators...

Do you believe that such media is so subtantially better as to be able to generate more plant yield and/or better quality as to surpass an equivalent three growbed flood and drain aquaponics system??

The capital costs might be essentially the same between both comparative systems, but would the "inputs" be as comparable??

i.e What cost is involved in either generating or purchasing the soil/compost as opposed to pellet feed??

Would maintenance, handling and labour cost be comparable between the two systems??

What risks to fish and/or plant health might be introduced by the soil/compost media... and how would you identify and control these risks?

And if the bottom line is to determine the most efficient utilisation of a given area to maximise return on capital investment.... how would this compare to other traditional growing methods ... such as NFT hydro??

Oh.. I forgot to add... given the "wicking" nature of the double-decker growbeds... and the slow drain/slow flow/slow overflow of the bottom water reservoirs, which I assume then return to the fish tank...

Do you think this will significantly impact on oxygenation throughout the system, possibly to the detrement of the fish??

And how will you filter out any soil/compost particles from returning to the fish tank... although I suspect your bottom reservoirs will in fact act as settling tanks due to the low inflow/outflow... which in itself generates a maintenance requirement...

Not to mention the Anarobic areas that may be created by the soil/compost. Roto mould machine and plastic feedstock etc. = Large capital investment.
I figure you did some experimenting already to consider this...
Come clean tell us what you found

Let's first come clean on the Masters Student. He is writing his thesis on supplementing our Winter heating requirements with compost or solar so he'll have nothing whatsoever to do with the "hybrid" system that I'm throwing around. I am also starting a new thread soon about an interesting "liquid solar insulation" technique that has been brought to my attention.

As far as the other questions, I'm not really trying to prove anything other than "is there another way of doing this and how does it compare to full AP or NFT Hydro" Like all my ventures, this will be tried small and if it looks promising, I'll be out looking for a benefactor to finance a full-size commercial system.

All I am looking for is "slightly better" plant growth and fruiting at this stage.

As far as the anaerobic areas and the "settling tank" question, yes I've thought of that and I have a simple drain valve to regularly flush the lower tanks and I've always believed in oxygenation to the point of saturation for the benefit of both my fish and plants. Little bit more power but worth it in the long run.

Rupe, thanks for your comments, they are thought provoking and really summarise the issues involved.

Good luck, I think you are onto something just may not be as easy to control. Water clearity may be a tradeoff but if the fish are healthy it may be worth it. Please keep us informed. For every problem there is a solution. Thanks for shareing your out of the box ideas. The research and development at the plant where I work just sold some injection/blow moulding machines to a local dairy. They build these small scale machines for plastic product testing them sell them when its proven out. We only make the base products so the only thing I'm familier with is extruders/expellers. With the economy stagnant like it is you may come across some deals with all the idled/cutback plastic/chemical plants.

Likewise, I look forward to seeing what you come up with and the results Synapto...

I'm sure you'll apply the same energy and ingenuity to these experiments as you did/have to your previous ventures...

Please keep us informed....

The liquid solar insulation idea sounds intriguing... is it based on phase change of liquified salt compounds... like a solar pool...

Well I am truly blown away by your system and very happy that you live just up the road (relatively speaking) from me so I will hopefully get to come and see your system first hand one day. I live a few kilometeres away from the roto tank factory close to Sahldana and he is keen to take on new projects for his production facilities if there is promise of enough numbers. Perhaps he could do the rotomoulding for you. I can send you his no if you are interested. I was trying to see if they had tanks that are reject on the top that I could buy for cheap and chop for FT and GB but sadly not many rejects . Please can you tell me where you got your blue barrels locally? I have been looking but so far not much luck.

Hello Synaptoman,

First I would just like to say that I am extremely impressed with everything you have accomplished in AP, and I look forward to following your future endeavors. As far as the subject of sex reversal goes, I found a link to an interesting PDF at FASTonline: http://www.fastonline.org/images/manuals/Aquaculture/Tilapia%20Information/Introduction_to_Tilapia_Sex-Determination_and_Sex-Reversal.pdf. If I knew how to copy and paste from a PDF, I would quote the pertinent paragraph, but I don't so I'll just summarize. According to the document, it is possible to feed estrogen to young fish to produce "morphological female, but genetic male fish" that can be "reared to maturity and then mated to normal male fish." The goal of course being a hatching of all male fry that haven't been treated with hormones. Has anyone on the forum tried this yet, or know where more information can be found on it?

"A novel variation on this scheme is to feed young fish estrogen. This results in a population
of all female fish. The morphological female but genetic male fish are then reared to
maturity and then mated to normal male fish. The resulting fry have a male father and a male
mother and thus will all be male. These young have never been treated with any hormone.
Of course this technique requires several years to develop the stocks and extensive progeny
testing to determine which fish produce the all male young. Even more complicated breeding
plans have been developed to fix breeding lines of male with two male chromosomes that
will always produce male offspring."

Very interesting. I had thought that genetic male females + genetic males would produce 25% females, 50% males, and 25% YY males (and the text supports that, from my cursory reading). The idea of creating YY males that could then be bred with any type of females to produce all male offspring is very interesting. I wonder if YY males would be fertile? Could the YY vs other be determined through a cheap genetic test or a sexlinked characteristic?

Sorry about the hijack, Synaptoman.

NO, please continue, I'm intrigued.

RE: growing power and their wicking beds.

My understanding is that they have double-decker beds, as mentioned before. The lower bed is a "traditional" gravel bed, and are used to grow water cress, microgreens, sprouts etc. These also act as the bio filters.

The upper level is the compost/wicking level. Here the higher-value crops are grown, like tomatoes. I don't believe this level has gravel, it's a constant stream of water. Into the water are placed pots that have holes drilled just at the water level, so a bit of water "laps" into the pots, and is then wicked up into the growing medium. The water that is wicked does not return to the system, there is no flow back from the compost-side.

The compost adds nutrients, I'm unsure of the other reasons to use it, except they produce a truly massive amount of compost there.

They're raising 10s of thousands of tilapia and yellow perch each year, and have a full-time aquaculture-ist on-staff.

Growing Power averages something like $200,000 USD/acre/year, and are growing nearly 160 different crops. Will Allen is a serious businessman. You can bet, if he's doing it, he's got a VERY good reason.

I have the plans for his system somewhere. Once this place is organized a bit more, I'll see if I can find them.

I'd be interested to see these plans.

What happened? Did this thread just die? It's been so interesting so far!