Mar 30, 2022

Today, I would like to talk about aquaponics. For those of you who are not exactly sure what that is (I must confess that I didn’t until I was convinced to give it a go), it is a combination of hydroponics which is growing plants in nutrient rich water and aquaculture which is growing fish for harvesting. The concept is that we grow the vegetables in an inert matter (that’s techo talk for expanded clay pellets or rocks). The plants need a water bath that will keep them fed and their roots moist – in hydroponics you must keep adding nutrients to the water to feed the plants. In aquaponics, we rely on the fish excretion to provide the necessary food for the plants.

 You need two separate containers, one to hold fish and the other is filled with clay pellets (lighter than rocks) to grow the plants in. The fish are fed with fish food or edible water plants and then they do their business in the water. This makes the water nutrient rich – instead of putting the water through a filter like you would in an aquarium, you pump the water into the container holding the clay pellets and plants. The clay pellets filter the water and retain the nutrients, the plants root system collects the nutrients they need from the water and clay pellets. The filtered water is then cycled back to the fish tank to start the process again.

 It sounds really simple, doesn’t it?

Not really… I’ll tell you how I did it for a minimal outlay. I was able to buy two fibreglass bathtubs from the local tip shop. I had some concrete blocks at home and a box of plumbing and irrigation bits in the shed. I sealed the plug hole of the tub for the fish tank and then set it on levelled ground under our carport. I then placed the second tub on the concrete blocks so that it was high enough off the ground to sit above the fish tank, overhanging a bit so that the water can drain back into the fish tank.

After researching what a Bell Syphon is and how to make one, I used that box of “leftover” bits from the sheds, I found enough “treasures” to get me started – see the orange table. The Syphon is installed in the drain hole of the grow bed. Use an old pond pump to get the water pumping from the fish tank, and into the grow bed. You will need a bit of trial and error to get the water levels right to activate the syphon at the right time…

 In the photo to below, see how I have the water from the Bell Syphon is hitting a sheet of stainless steel, this “cascading effect” helps to aerate the water for the fish tank. Last thing you need to do is find a submersible pump from an old fish tank or garden pond and set it up so that it pumps the water from the fish tank into the garden bed.

 Fill the garden bed up with clay pellets so that they are about 2cm above the point where the Bell Syphon starts to empty. (The water in the garden bed needs to empty quick enough to ensure that the Bell Syphon resets allowing the garden bed to fill up again so there will be a bit of adjusting the flow rate of the pump required.) You are now almost good to go. I put some liquid seaweed in the water to give the plants something to feed off while the aquaponics system starts creating its own good bacteria for the plants. You will need to do a bit of water quality testing to make sure it is ready to add your fish into the system. We have got five goldfish working for us at the moment, depending on the climate in your area, you can use trout, silver perch, even Murray cod! That way you can harvest fish to eat too! But don’t forget to keep restocking the fish for an ongoing supply.

I made a cover of hail netting to go over the grow bed to keep the local wildlife out and then wondered why the leafy green vegetables were growing well but the flowering ones like squash and tomatoes did not produce… then it occurred to me that not only did the hail netting keep out the undesirables, it also kept out the pollinators too!!! Oh well, you are never too old to learn…

There is a Facebook group called Organic Aquaponics & Backyard Harvesting wich is run by The Aquaponics Lady Candy Alexander from Brisbane. She is very knowledgeable and her Facebook entries are very informative so if you want some more info, perhaps pop over and have a look.

That’s it for now; off to check on the worm farm… might talk about them next time.

Pa Kettle

P.S. Just a little thought before I go

“When people talk about 30 years ago, I think they mean the 1970s, but actually they mean 1992! Oh dear, I think I need a lie down…”

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