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Humbug's "open-Loop" Aquaponics


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#1 humbug

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Posted 11 November 2015 - 09:24 PM

I’m documenting the build of my new fishroom on another thread, but thought I’d share another our recent projects - our fish-poo powered vegetable garden.

 

I currently have two small fishrooms running, with the third fishroom under construction.  My original fish room was established in our cellar, and the second room is a partitioned off section of one of our sheds.  I’ve always been concerned about the amount of water I use for water changes and was keen to put at least some of the waste water to use.  The plan was to build a series of terraced wicking garden beds outside the shed to use at least a portion of the water from that fishroom, and grow some vegis. 

 

To date we have one bed up and running, and a second bed was partially constructed before our attention got diverted to all of the other crazy projects in our life!!!

 

If you haven’t come across the concept before, a wicking bed acts like those self-watering plant pots, with a reservoir of water in the bottom.  The water wicks up through the soil to the roots of the plants.  Because there is little evaporation, they use far less water than a garden bed which is watered from above, and even in the most extreme heat-waves we have found the sump only needs topping up once a week.  This works in brilliantly with my fishroom water-change schedule!! 

 

In the past we have always been hopeless at growing vegis.  We are never consistent enough with watering.  This system makes it EASY!!!  It’s also great when we go away for short holidays – no need to worry about the vegis going without water.  There are plenty of good resources on the net with info on building wicking beds – worth doing some reading if you think this might be for you.

The shed is at the top of our block, and the ground drops off fairly steeply towards the house.  We have terraced the first two beds into the slope.  Waste water leaves the fishroom via a drain which runs directly into the sump of the upper bed.  Once the first sump is full, the water will overflow to the sump of the lower bed, and that then overflows on to the surrounding garden.  We have the scope to add a further two beds later.

 

Constructed wherever possible using recycled materials, the structure is hardwood posts from a demolished building, and 130 year old corrugated iron from the roof of a historic building.  Each bed is 5.3m long x 1.6m wide.  One wall of the bed closest the shed is a retaining wall built from cement sleepers. 

The shell was built, and a layer of sand placed in the bottom before installing the pond liner which covers the bottom and extends up the walls of the structure. 

 

 

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We placed a layer of old carpet below and above the pond liner to help protect it from the gravel which fills the sump.  On top of the carpet went the plumbing.  A ring of perforated agricultural pipe allows the water from the fish room to fill the sump.

 

 

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Then we added about 300mm depth of gravel on top, covered by a layer of geotech material to allow transfer of water but stop the soil mixing with the gravel.  Then the soil went in, with a lot of compost and manure mixed in.   The sump was then filled with water.

 

In the middle of a heat-wave we planted the first crop of vegis and herbs - tomatoes, capsicum, squash, cucumber, zuchini, celery, beetroot, basil, oregano, mint and parsley.  We watered from above daily for about the first week; just until the plants roots had developed enough to reach the moist soil.  After that – the plants were on their own!

 

 

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We are still experimenting a bit.  We haven’t added any fertilisers at all to date.   I use buffers and cichlid salts in my tanks, so the water going into the beds is hard and alkaline.  They say you need to be careful what you put into a wicking bed in the way of ferts because it’s effectively a closed system. It will be interesting to see how it goes longer term with the fishroom water.

 

The vegis had absolutely no attention at all right through the hot spells of the first Adelaide summer. The sump was being re-filled every 7-10 days, and that’s it. No fertiliser was added, other than that coming from the tank water changes. Even through the hottest weather this one bed was using less than 100 litres of water a week.

 

 

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The bed is in dappled light in the morning and full sun in the afternoon. It’s very close to the corrugated iron of the shed, and the plants closest to the shed didn’t do quite as well. We suspect that they were just cooking. Summers here are hot –we had one day with a max temp recording of 45.9deg, and then 44.8deg less than a week later. But the wicking bed meant that the plants have constant moisture level in the soil all the time.

 

What amazes me about this system is just how little work it takes to grow vegis. The water from the fishroom goes straight into the sump on water change day. Other than pulling a very occasional weed, all we’ve had to do is pick the vegis.

 

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Winter vegis weren’t as successful due to our total neglect when the pests arrived.  :mellow:

 

Last weekend we planted another crop of summer vegis – tomatoes, capsicum, squash, cucumber, eggplant, zucchini and a few herbs.  When we get a spare day away from the bakehouse build we will get the second bed up and running.

 

 

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I'm VERY impressed with the wicking bed method, based on what I've seen. I think it’s a good compromise - many of the benefits of aquaponics without any risks to the fish. Only problem is that I'd need a hell of a lot of these beds to go anywhere near using all the water from the fish room!

 

 

Even without using fish-water, these beds are the way to grow vegis.  Once you have tried this I can assure you that you WILL be a convert!!!!  As well as the second similar sized bed which is already partially constructed, I’m looking to set up a smaller version to run as a worm farm, again using the water from the fishroom.  We have room for a total of four of the big vegi beds if we decided to build them in the future. 

 

 

Plans in train for use of the water from the Bakehouse Fishroom too, but that’s another story . . . . . .



#2 BengaBoy

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Posted 12 November 2015 - 08:32 AM

excellent humbug

 

can you tell us the depth of  the soil? I see where you said the gravel was 300mm. Just wondering about the wicking effect versus depth.

 

back in a past life I used to put the fish tank water onto my garden beds but the natives hated it - too nutrient rich I think. vegies sound ideal.



#3 humbug

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Posted 13 November 2015 - 09:36 AM

Its a while since we set up the first one, but from memory the walls of the bed are around 700mm high.  We used 300mm gravel and 300mm soil, leaving around 100mm of freeboard to help hold the mulch in.  When we set up the next one I'll try to document it a bit better with photos. 


Talking to a guy who has dabbled in aquaponics using higher pH water, he suggests some veggies will do better than others.  Brassicas should do well, and tomatoes seem to thrive.  I just wonder if we might end up with a build up of salts over time, but time will tell.



#4 humbug

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Posted 13 November 2015 - 09:52 AM

Just stumbled across this great little video on setting up a wicking bed.

http://www.abc.net.a...es/s4010599.htm



#5 Stormfyre

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Posted 13 November 2015 - 04:02 PM

Good vid.



#6 BengaBoy

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Posted 13 November 2015 - 04:19 PM

30cm seems to be the magic number for the soil depth.

 

in the video the overflow looked a bit problematic? a minor quibble :)

 

looks to be a great idea - will be a while before I can get around to trying it out tho.

 

thanks humbug






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