As bio-diversity is important for the health of the overall permaculture design, those little systems/methods that we produce food should also be diverse. I call it “system diversity”. The diverse systems increase the resilience of the design. And resilience gives us an ease of mind when it comes to food crisis and certainly provides a more nutritious diet than available.
One of these systems is aquaponics which combines fish and vegetables in a closed loop system. Fish produce fertilizer and plants use this fertilizer to grow. The yields are a good source of protein (as in fish) and abundant amount of vegetables. Fish and vegetables live in a symbiotic relationship.
I’ve started doing aquaponics about 4 years ago. There was also an "idea incubation" stage for about a year before that.
I was running 2 little simple setups for the last 4 years in my backyard. First one was housing silver perch and the second one was trout. Fish tanks and grow beds were cut from IBCs (Intermediate Bulk Container) as commonly preferred by backyard aquaponics enthusiasts.
These systems didn’t have a dedicated filter. The only biological filter was media grow beds (volcanic rock filled growing beds). I have harvested many trout from one system and my silver perch are still growing. Silver perch is a semi-tropical fish and they grow slowly in Canberra’s winters as they don’t eat much below 14 degrees Celsius.
It was time to design a proper system to accommodate a filter, gravity fed media beds, a sump and expandable grow channels. I was reading forums, looking at 3D designs and, watching YouTube videos for a while and have a pretty good idea of what I want and how to fit into my tiny suburban space. There are countless free and quality information on the web when it comes to aquaponics design and management.
After much thought, this was the plan I came up with:
This plan is consisting of 1 fish tank 1000L (FT on the left), 1 settling filter 250L (RFF/SUF - Radial Flow Filter, Static Upflow Filter), 4 grow beds around 320X4=1280L, 1 sump tank at 400L (ST) and 3 NFT (Nutrient Film Technique) channels. There will be an additional duck weed and azolla bed later. There is only one pump to circulate the water from sump to fish tank and the rest is fed by gravity. This is the most economic design from the electricity consumption point of view.
Picture above is where I am going to squeeze the setup. The green/white box at the back is the insulated fish tank and from fish tank to the end of the sump tank, there are 5 meters to fit everything. The fence will hold the grow channels in the future utilizing the vertical space.
When it comes to hardware many things can be bought from second hand online shops. IBCs, barrels, pumps can all be supplied cheap. You have to make sure no harmful chemicals shall be carried in them. Plumbing and fittings are from the big box warehouses. The barrels I used bought from an old Italian wine maker. The large one became the filter and the small one my compost tea brewer.
I had to sacrifice one of my raised veggie gardens to accommodate the sump tank. I removed the box and dug in the sump hole, I realized that there is a large clay rock underneath and I couldn’t dig in further. It filled in at first rains and stayed full for a long time. There was even a frog croaking at night looking for a mate in there.
I then built the stand to carry the grow beds. I only used what is available in the garden and my garage. Legs are iron bark slippers and some pine timber for structural integrity.
I am using my insulated full IBC as my main fish tank. There will be a %30 shade cloth on top when I have time. This fish tank holds 1000L of water and the water level never goes below that. Even if the water pump fails or sump tank goes dry, the fish should be all right for a while. I needed to lift the fish tank about another 30cm by supporting the legs so that I could use the gravity to feed the rest of the system. This was a monumental job but for the overall reliability of the system, it was required and recommended by our lovely BYAP (BackYard Aquaponics forum members.
I situated two air stones in the fish tank fed by an 80L per minute air pump. This air pump is working only during the day and turned off with a timer during the nights. It is not noisy and works well. I need to change the O ring from time to time as an ongoing maintenance. Its diaphragm is available online if it ever fails. As my choice of fish is trout, an air pump is a must to provide enough dissolved oxygen.
There are 2 different air hoses I bought. One from the aquarium shop and one from the internet. The one I bought from the internet couldn’t stand the sun and became sticky and perished. The aquarium shop jobby is still running under sun and didn’t fail. Paying a little more money for quality pays off in the long run.
Having a powerful air pump, I can now prepare the aerated compost teas in a 250L drum for my garden and wicking beds. So it is a win for me.
Water from fish tank goes into a filter via a thing called Solid Lifting Outlet (SLO). SLO is a 40mm pipe that goes down to the bottom of the fish tank. Top of the pipe connected to a T which goes out at the level where you want the water height to be. One side of the T is open to air so that SLO doesn’t work like a siphon. The bottom of the SLO is closed with a cap that has holes on it smaller than the fish fingerlings so that they are not sucked in and travel into the filter from there.
I am actually amazed how the fish tank is staying clean and there are no debris at the bottom. SLO pulls all the uneaten food and fish poo that sinks to the bottom and keeps the FT clean.
SLO feeds into a mechanical settling filter via gravity. This filter is made from a 250L plastic drum with an inner pipe that leads the water to the bottom. While water goes down, the solids settle at the bottom and upper columns of the water relatively free of debris. There are still suspended solids but that requires another filter which I didn’t build called Static Up-flow Filter.
All these filtering keeps the media grow beds clean and rather than doing a maintenance on grow beds every year, you can do it every second or third year depending on your filtering capacity and fish density.
There are also red composting worms in my grow beds that take care of any build up or rotting roots.
Settling filter still needs to be cleaned regularly but relatively easier then cleaning the media grow beds. The sludge settling at the bottom of the filter is an oxygen sink. The sludge pulls oxygen from the water. Cleaning the filter once a month depending on your fish density and accumulation of solids is a necessity.
Actually, I can use the sludge that comes out during the cleaning of the filter and oxidize it in a separated container for two weeks by applying air and use it in the system as an additional fertilizer full of minerals but I am using the sludge under drip lines of my fruittrees and it is working perfectly. Also you can activate charcoal with this sludge and turn it into active biochar for your gardens or you can dump it into your worm farm to increase the quality of the black gold.
Adjusting the height of the filter required couple of palettes. The bottom palette came from a friend and reused. The little top one was lying around the garden and used for other things before ending up here.
Using an exit point from the filter that is above the grow beds, the water flows into the grow beds via a 40mm pipe. This water is full of nutrients dissolved in water minus the big particles.
Once the water trickles into the grow beds, the nitrosomonas bacteria turns the ammonia (NH3) to nitrite (NO2) and the nitrospira bacteria turns the NO2 to nitrate (NO3). This happens in a highly oxygenated water hence the necessity of an air pump. Media (scoria) filled grow beds are acting a like a giant bio filter.
Media grow beds managed in couple of ways, either with a bell siphon, constant flood or a timed constant flood. These 3 methods are based on your requirements and practically there is no difference in between them in terms of plant growth. If you are trying turmeric or ginger (root vegetables) you might want to go with bell siphon though as the root vegetables may rot in the constant water.
I have 4 grow beds filled with volcanic scoria and some LECA (Lightweight Expanded Clay Aggregate) on top 10cm. But the LECA mixed in after the first harvest when I am pulling the roots out of the grow beds. LECA is expensive and scoria is cheaper but when it comes to cleaning the grow beds after 2 years of operation, LECA wins hands down.
As soon as the system circulating without any leaks, I put in the seedlings and seeds. In just 4 weeks the growth was astonishing. I am also thinking of integrating some perennials like a passion fruit or grape in their own buckets.
Grow beds also act like another bio-filter and cleanse the water. I could have gone with a Deep Water Culture (DWC) and get rid of the scoria all together but this would have reduced the resiliency of the system and I would have to build another filter or two to remove the suspended solids and oxidize the ammonia with a Moving Bed Bio Reactor (MBBR). At this scale, I am okay with my setup and there is no need to complicate it more than it is necessary.
All the grow beds connected to a 100mm pipe which takes the water to a sump tank (ST). In the future I can punch some holes on this pipe and grow strawberries too.
Sump here is another settling tank. It keeps the water level in fish tank at a constant level. Also it is the home to my red koi. The one and only water pump is also in the sump tank.
I also have oyster shells dangling in a plastic net which I’ve heard from Geoff Lawton for the first time to adjust the acidity in rain water systems. If the acidity increases (pH goes down) these shells will dissolve slowly to adjust acidity.
All the tanks and grow beds are insulated with an aluminum coated reflective sheet (roof insulation) which protects the HDPE liner and prolongs its life. It is also important to protect the water from sun as it grows algae. Algae is not a preferred food in a closed system like aquaponics. We need to keep water as pristine as we can so that fish are happy. Especially for silver perch and trout water chemistry and cleanliness is utmost important. Fish like carp, red fin and tilapia doesn’t care much about the water but if you want to eat the fish eventually, keep the water clean so that the taste of the fish is better.
For the moment I don’t have any Nutrient Film Technique (NFT) channels. These are 100mm pipes or gutter like channels. There are holes punched on it at certain intervals and little plastic baskets inserted. You can grow e.g. strawberries, lettuce keeping them away from the roly-polies (Armadillidium vulgare) and slugs in these channels. This will be a later extension for my alpine strawberries.
As a result, I am happy with this setup and can grow 40 trout a year without a problem and of course vegetables continuously. I don’t think I can extend the system any larger. My space is very limited. Trout grows in about 8 months to plate size. We are getting the trout around March in Southern Hemisphere as a fingerling.