So, it has been a long few months of building, then a longer few months getting the water quality to stabilise, but its finally working! 1000L fish tank, ~100L sump (i.e. a bathtub), 120 little pots, 1 big pot (with a makeshift float valve), some DIY drip irrigation and a bunch of happy plants.
Some insights
- A biological filter (bio-filter – i.e. some crumpled up shade net in an old pool filter) makes for a good bacterial home, but is still not good enough to settle out the solid waste. A two stage filter is definitely a must.
- Using 110mm PVC pipes in this configuration (i.e. Nutrient Film Technique – NFC) makes for an excellent solids settling zone. Not so great for root health though.
- Algae reduction mechanism is not completely known, but getting the nitrifiying bacteria population up and running in the bio-filter was likely the culprit.
- Adding and active population of Egeria densa with some aquatic snails seemed to accelerate water stability and algae reduction.
A walk-through of the build
This scale-up of my aquaponics prototype has been an interesting build to say the least. Using mostly parts from old projects (flowbins), a steel frame used on one of the old bakkies, a couple of old bathtubs, and an old pool filter (without the sand) and part of an old garden in a plumbing business’ yard, I made an aquapoincs system to grow a variety of plants. Some new parts were required: a fountain pump, air pump, two aquarium heaters, a makeshift roof (shade net), piping, valves, and associated connections and reductions. A concrete slab with a small retaining wall was also needed to hold the tank. Lets step through the process of putting it all together.
Preparing the site & planting areas
Site before any development.
The old garden where the new aquaponics will be built
Preparing site for aquaponics.
Cleared and leveled site. The ground where the platform will be was compacted with a hand stamper.
Platform preparation area.
A small trench was dug in front of the platform to ensure the retaining wall was stable.
Retaining wall for concrete slab.
Bricks were laid to form the retaining wall for the platform.
Freshly placed concrete slab.
Concrete platform was about 7cm. Additional dirt was added and stamped before laying the concrete slab.
Shadenet frame placement.
Pillars were put up with 110mm blue, and 50mm white pipe. These were buried around 30cm deep, with a height of around 2m from ground level.
Test placement of frame, filter, and tank.
Some 40mm black irrigation pipe was used as ribs for holding up the shade net. The tank was placed, and the frame was placed but some minor changes were still needed.
Aquaponics NFT and big pot in final positions.
The shade net was secured using some plastic string and tied to some stakes in the ground.
Aquaponics sump connected to fishtank.
Pictured here is the piping of for the tank and sump. The pot and the NFT pipes are placed.
Sump made from two bathtubs.
The sump (two bathtubs – one to hold water, one to cover) collects any overflow from the tank or NFT pipes. The pump inside takes water back to the tank.
Big pot with drainage pipe.
The inside of the big pot (half flowbin) where 110mm drainage pipe was cut and placed to form a water reservoir inside the pot.
Pipe for float valve.
A 200mm PVC pipe was placed vertically in the pot to provide access for a water feed controlled by a float valve.
Big pot before planting.
Big pot, with drainage pipe, lined with geo-textile and covered with local and potting soil.
Drip irrigation connected to aquaponics.
One of the last connects was a 20mm in a ‘T’ connection and 5mm soft irrigation pipe with holes punched in it feeds the garden directly.
Drip irrigation garden bed.
Another view of the drip irrigation showing how the 20mm spreads the water over 8x 5mm pipes with holes in them.
Float valve before placement in big pot.
a float valve was used to control water entry into the pot. It was reused from old stock and fulfilled its purpose well.
Planting & stabilising the water
After months of waiting and trying to stabilise water using different aeration, water cycling and planting strategies, the water finally stabilised after the addition of a floating plant (Egeria densa) and aquatic snails from my smaller fish tanks. There is still some doubt whether the water quality would have stabilised eventually by itself, but I have been reading a lot and there are many factors that can lead to stable water. Since I cannot do water quality measurements yet, I have to do it by eye and intuition. The success of E. densa in the tank leads me to believe that the addition of these plants helped slow down water flow, settled the algae, intercepted some light, and reduced nutrients in the water. The snails ate any remaining algae and turned into nice solid waste that could more easily settle. Once the bacteria in the filter got up and running, the solid waste breaks down and gets fed to the plants and then I got some healthy growth happening.
Greenhouse with fishtank inside.
Fish tank in place with greenhouse and NFT pipes in the process of being made.
First guppies in fish tank.
The fish (guppies) were added just before winter and left to test the conditions. They were fed daily, except on weekends. The algae buildup is clear and indicates the water has not stabilised.
Drip irrigation garden bed.
Another view of the drip irrigation showing how the 20mm spreads the water over 8x 5mm pipes with holes in them.
Newly planted pots in NFT.
The 120 pots in the NFT system with plants beginning to germinate.
Fish tank with guppies.
Hungry guppies in fish tank with clear water.
Close up of fish tank with plants and fish.
Water is a lot clearer after 2 months and the addition the Egeria densa and snails.
Greenhouse, fishtank and NFT.
The small greenhouse in the background feeds to the filter, then is spread to various taps that feed the NFT pipes, drip irrigation, and future planting areas.
Close-up of spinach sproating from NFT.
The growth of spinach in the NFT pots showed improved growth after the water cleared up.
Big pot with garden bed in background.
The pot and drip irrigation performed well and had some really good growth.
Close-up of big pot.
The big pot is fed by the outlet pipe from the NFT pipes. A float valve (bottom left within pipe) regulates the water into the pot.
Side view of NFT with new drip irrigation.
The site next to the aquaponics greenhouse was cleared and a drip irrigation system was put in.
Nutrient Film Technique after 3 months
Plants showing much better growth after the water cleared up. From right to left: spinach, basil, thyme, onion, spring onion, and lavender. Onion and spring onion did not show good growth in the NFT system.
Drip irrigation fed from worm digester.
Drip irrigation using 20mm pipe with holes. Fed from a flowbin that was converted into a earth worm bin. Above the earthworm bin is a small scale constructed wetland.
Improvements
This system took way longer than I expected to stabilise and to see good growth. A second stage filter to help with the solid waste in the NFT seems to be a necessity. Making the solid waste accessible for other uses would be a big plus too. The drip irrigation could be improved as the dripping was uneven, the DIY side of things has its pros, but this is definitely a con. The growth in the garden bed was amazing and I see a lot of potential in drip feed irrigation from aquaculture waste water (see Fertigation). The balance of fish to plants also could be improved, but with the recent rains, and less water changes, I am getting good growth all round. My thinking is that more plants of different types, as well as integrating more organisms like giant river prawns, in addition to Tilapia would make the system more productive and more resilient to changes and disease.
To improve the stability of the water, either I would need to purchase microbes to inoculate the system, or figure out how to take from my existing aquaponics systems. I think some of the growth media could be a good inoculum, but it would mean getting enough of the medium together to make sure the system is inoculated quickly, or at least faster than a few months.
Future work
Now that I have a larger prototype and I have spoken to a few people, the next challenge is getting a salable product. All the nuts and bolts, services, and possible sizes of custom system formed into a product. Finding suppliers for tanks, fish, plants, sensors, feed, pro-biotics and more. Integrating these systems, getting feedback and making this system as simple as possible are key considerations for me right now.
The conversations I have had with other small business owners seem to point to high prices, expertise, and low value of products as some limitations of aquaponics in South Africa. However, our agricultural sector is very large and many products are available for agriculture in general. As more awareness of diverse sets of products improves so will demand. Some exciting areas that are emerging are medicinal plants, biogas, algae, and turning waste into value (the circular approach to production). Many different technologies are emerging that I hope to cover in future posts.
I wholeheartedly endorse every idea you’ve outlined in your post. They are undeniably persuasive and will undoubtedly be successful. However, the postings are rather brief for novice readers; could you kindly extend them slightly in the future? I appreciate the post.
Hi there. Thank you for your comment. I would be happy to say more on this project, if you want me to mention anything specific, let me know and I will try and include it.
It has been operating now for almost a year and seems very stable. With the power and water interruptions this has been a big surprise. The fish population has stabilized because of this and I am looking into making this system more independent from the grid. But as always it is expensive.
Your ability to distill complex concepts into digestible nuggets of wisdom is truly remarkable. I always come away from your blog feeling enlightened and inspired. Keep up the phenomenal work!