The second winter - Backyard Aquaponics in Melbourne

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The winter aquaponics

The winter is here in Melbourne

This is the second winter since I started my backyard aquaponics and I want to share my experience and how I manage my system and still grow fish and veges throughout the year.

Melbourne winter can be chilly and the temperature could go down to 0 ~ 3°C and in the early morning and 8~ 12°C during the day. It is an ideal temperature if you grow trouts as they thrive and grow well in a cold climate. Jonathan from Melbourne Aquaponics recommends growing trouts during the winter as you can harvest them in 6 months (Apr ~ Sep).

How I failed last winter

I started my aquaponic system with 5 Gold Fish and 15 Silver Perch fingerlings at the beginning of the last winter. The Gold Fish were great to start aquaponics for a beginner like me as they were more tolerant than other fish in terms of temperature, pH and ammonia. I got medium size in a local aquarium shop and introduced them as soon as my system was ready.

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5 Gold fish as a starter

I observed the system for over 3 weeks and monitor pH, ammonia, nitrite and nitrate level with a test kit. Everything looked good and I went to buy Silver Perch fingerlings.

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I observed the system for over 3 weeks and monitor pH, ammonia, nitrite and nitrate level with a test kit. Everything looked good and I went to buy Silver Perch fingerlings.

The Silver Perch, another popular Australian native fish for aquaponics, should be able to survive Melbourne winter, as they live in Victorian water, however, they prefer the temperature above 10°C.

My first 15 Silver Perch fingerlings, which I bought from Jason found in Gumtree, weren’t happy from the beginning compare to the Gold Fish. They were hiding at the corner and hardly moved and I couldn’t even tell if they were eating food.

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Silver Perch Fingerlings

After 2 weeks, I noticed 1 fingerling died and floating on the surface. I initially thought there would always be weak ones in a batch and not all of them could survive, just like anything else. I was wrong. I found another one floating next day and that continued every day.

I checked the temperature, pH and ammonia and see what went wrong. The water temperature was around 8°C, 7.5 pH and 0.25 ppm for ammonia. In general, according to many aquaponic system instruction on the Internet, the pH should be between 6.5 ~ 7.5 and ammonia should be 0 ppm, while temperature really depends on the kind of fish. I couldn’t tell what actually caused the death so I went to a local aquarium shop for help.

The bacteria thrives in warmer temperature

The guy told me the combination of the pH and ammonia level are the problem. The ammonia level must be closed to 0 as it is just toxic to fish. The pH should be around 6.8 and higher pH makes ammonia much more toxic to fish. While Gold Fish could survive in the water, Silver Perch fingerlings are too small to live in the toxic water.

The cause was simple. It was too cold for bacteria to be active to breakdown the toxic ammonia to nitrite and then nitrate. I also didn’t even have enough veges growing to consume nitrate. Here is my summary of what went wrong

  • Transferred fingerlings into the tank straight away — it is stressful for fish to migrate to new water and the new water should be added into a bag, little by little, over a day
  • It was too cold for Silver Perch fingerlings to adapt the rapid environmental changes and cold water
  • It was too cold for the bacterial to be active, which left ammonia in the system — they thrive the temperature between 17 ~ 34 °C and much less active below 10 °C

Heater Installed

The recommendation was to install an aquarium heater. I bought EHEIM thermocontrol 300w, a German brand and costed around $60. This heater was submersible and you can just attach on the side of the fish tank. It needs to be on all the time in order to control the temperature efficiently.

Installing this heater wasn’t ideal as the heater consumed a lot more electricity. I liked the idea of aquaponics as ‘it is a sustainable growing system with low maintenance and cost’.

My system so far used a submersible water pump (7.5 watts) and an air pump (2.5 watts), total of only 10 watt. The heater added 300 watts extra power usage throughout the winter! 300 watts were a lot more than an average fridge (100 ~ 250 watts).

The result is however immediate and effective. At this time, I only had 5 Gold Fish left in my water tank but they became so active and happy and you couldn’t even follow them as they swam so fast!

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Heater installed on the side of the fish tank

Setup Insulation and Dome Ceiling

My goal was to establish a sustainable backyard aquaponic system, which produce veges and fish, cheaper and better result than the soil based veggie garden. So I had to find more efficient heating system.

I researched on YouTube (which was the source of many backyard aquaponics ideas from around the world) and found people with a cold climate would make a system inside or in a greenhouse. I decided to setup a greenhouse.

First part of my green house system is to insulate the fish tank, so I can minimise the heat loss. I went to a local fish market and collected polystyrene fish box lids and covered the entire fish tank. It looked ugly so I then wrapped them with jute bags.

The next step is to make a dome ceiling with PVC pipes and greenhouse films. I was heavily inspired by this YouTube video and there were all sort of DIY greenhouse ideas available.

The structure was very simple. I used 15 mm PVC pipes with Tees and elbows, they were all available from Bunnings. For a greenhouse film, I used a plastic cover for a queen matres I found in my garage. It was a prototype and my priority was to setup and test it first before further investing on a greenhouse film.

The greenhouse made the temperature a little higher than outside and also protected the veggies from the rain and wind. The veggies just looked happier after the ceiling.

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Handmade greenhouse

Reflecting the sun light

Another improvement I made was to get an extra sunlight by placing the car window sunshade. My aquaponics was setup behind a lemon tree and a crepe myrtle tree and we got less sun light during the winter. It will give extra sun light for veggies and made greenhouse temperature a little higher.

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Car Window Sunshade

The result of the first winter was better than I expected. I only had 5 Gold Fish to produce food for the veggies but I got 2 good size cabbages, 1 beetroot, a bunch of spring onions, lettuces, garlic and strawberries!

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The first year

The second winter is here

I waited for the spring to get more Silver Perch fingerlings, to just make sure they could survive. They were happy throughout the summer and I got a lot of veggies during the summer, including cherry tomatoes, Shiso leaves , strawberries, basil, mint etc.

The Silver Perch had been fed twice a day during the summer and they had grown significantly. Some of them are doubled up in size and around 12 cm in lengths.

We had some chilly mornings in May and the Silver Perch became inactive so I setup the heater. They became happy and swim well and eat well (twice a day) again.

I also improved the look of my system, by simply covered the fish tank with timber frame, inspired by Jonathan’s. The greenhouse will be setup next weekend.

The veggies for this year include broccoli, garlic, spring onions, spinach and strawberries and they were looking find so far.

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The second winter aquaponic system with a green house

Here is my story of the challenges of aquaponics in winter. Thanks for reading!

References (Where I learned all techniques)

Written by

Dad for 2 girls, software architect and a director of Nakanoya in Melbourne Australia.

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