A rambling description of the growth of our aquaponics system:
Our aquaponics system has been a labour of love and remains a work in progress.
It started as a proof of concept with a NFT (nutrient film technique) table given to us by our friend, David, a bucket of water and an aquarium pump to circulate it. We didn’t have any fish in it at this stage.
That worked, so we moved to the media bed idea. That took much, much more effort – construction of the supports, finding and cutting the beds, cleaning the media and, of course, the plumbing (many $$$$$ indeed!).
Then we added a few fish – a few donated goldfish in a single tank and they survived for a long time.
That second incarnation of the aquaponics was a greatly expanded one. This version consisted of the NFT table and 3 media beds, the fish tank and a sump. All survived the winter in a DIY greenhouse that the whole family got together to build from an old shade house frame and sheets of plastic.
Proud builders of our DIY greenhouse
Deciding that it all worked well, it was time to ditch the greenhouse as it was the end of Winter and add a fourth bed. The NFT table was given away later as well, to be replaced by bed number 5 and a second sump tank.
An extra tank was added to hold more water. It was planned to be some kind of sediment trap but it wasn’t effective.
Next came a pipe bed, running higher than the others along the fence at the back of the system..
Later we added a bed to hold lettuce and the like on a raft. This bed needed a constant flow because, with its addition, our pump didn’t have enough flow to satisfy a sixth bell siphon.
That bed was plagued with algae. To resolve it, it became a constant flow media bed where the water level is constant but the media that the plants grow in protects the water from the light, inhibiting algae.
Finally, four Dutch Buckets were added to the system, supplied by the flow from the pipe bed and dumping emptying directly into the sump. They did quite well be for Sweet Potato. We had issues with the roots of Sweet Potatoes in a regular media bed and ended up hacking them out with a hatchet and putting the media onto the garden.
The Dutch Buckets have been taken down and replaced with a single tub for the Sweet Potato and Wasabi. All the pipes and stuff made the area look untidy and I’d made a mistake with the type of bucket that I chose because it was cheap.. I didn’t realise that they were slightly translucent, allowing enough light to allow the growth of algae on the perlite inside.
We took the Dutch buckets out, they were an over complicated solution to a minor problem.
Our friend Nick gave us three huge plastic tubs and an IBC which we promptly chopped and flipped, converting the top onto a floating raft bed and a fenced off area for growing Azolla.
The water from the overflow of the IBC was directed to a bucket that contains filter material. The water enters at he bottom, where coarse particles settle out, then it makes its way up through three layers of increasingly fine material before exiting through an outlet into the sump.
This bucket filter is also where I add liquid fertilizers so that they are slowly and steadily mixed into the system water.As the filter flows into the sump, a lot more mixing with system water happens here too. Hopefully that reduces the shock of having a lot of chemicals hitting the system all at once.
The old fish tank was reused in the front yard and the IBC became the new tank. We bought a 5000lph pump and used one of the new tubs for he sump. The flow was simplified using flexible grey hose (as recommended by Rob Grey) and the pipes to the various sections beds were split so we don’t use the single flow to fish tank idea and rely on siphoning and overflow. This allowed a lot more customization of flow.
We added 12m of PVC pipe beds that could now be operated with the new flow rates.
Over a few days, we noticed the sump was too small and the pump was running dry. We put up with this for a month or so before investing in 50 litre storage tub to add holding capacity. That was still too small, so we went to 75l. The story was still the same so we went to 100l. This was still running a little low for me, no backup in case things went a bit astray.
We decided to bite the bullet and but a 200l pond tub that gave us more than enough capacity when added to the existing sump. It was pricey but the only big tub we could find that had a low enough profile to fit under the media beds.
Over the next couple of months, I added three Catfish to clean the fish poo at the bottom and 5 freshwater mussels which can filter fine particles in the water, filtering up to 100 litres each per day!
Here’s a brief video showing the nearly mature system at the end of Summer 2019 –
The 12m pipe bed along the fence didn’t work well. There was too much shade and the flow wasn’t great so plants didn’t thrive. It was shortened to 2 layers of 3 metres and some small remnants were attached to the wall of the IBC. I removed the sediment filter that was in that part of the system as well.
The filters on the inlets of the media beds kept clogging, I think because the material was too fine. I liked the filters where they were positioned so changed the material to blue aquarium filter foam. It’s coarser then the white aquarium wool I was using but doesn’t clog anywhere as easily, plus it’s easier to clean.
On the pipe bed along the fence, I removed the plant from the first hole and replaced it with a block of the same, blue, filter foam. That keeps this area nice and clean and is easy to remove and rinse.
Being all hyped on our pending success, I made an entirely separate second system along the wall of the house. This consisted of a 300 litre tank (it used to be the fish tank in an earlier incarnation of the big system and was then moved to the front yard to do duty as a supplementary rain tank) and a 6 m return of PVC pipe for the bed, This system is run from a 10 W aquarium pump and contains about 20 Goldfish, 2 Catfish and 2 freshwater mussels.
In between the pipes on this second system, I put the 3 plastic baby baths which are filled with perlite and are home to Carrot Herb, Brahmi, Water cress and experimentally, Water Chestnuts and Okinawan Spinach. These aren’t technically ‘aquaponic’ but are watered with water taken from the fish tank.
That’s how it stands now, in January, 2020. I don’t think I can make it any bigger as we are running out of space. I’d like to increase the size of the sump and upgrade the pump to a 6000 liter per hour one just to get a little more flow.
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