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How a Taupo primary school pool became a vegetable garden

Original Source here: Stuff CHRISTINE RUSH Last updated 05:00, August 20 2015

What do you get when you cross a former swimming pool, some keen pupils and a whole heap of goldfish? A highly productive aquaponics system.

Wairakei Primary School in Taupo has what is thought to be the only school aquaponics unit in New Zealand. Officially opened in May, it is the culmination of three years planning and fundraising, says teacher aide and Enviroschools leader Diana Fitzsimmons. 

The school used to have outdoor gardens but due to the chilly climate and light pumice soil, nothing grew.

"Adding compost and nutrients didn't help and they were costing a fortune," says Diana.

At the same time the swimming pool was decommissioned. The pupils came up with ideas for the space: a skateboard park, flying fox, spongeball pit, trampoline or garden.

"They went through pros and cons and how they would run them, and came up with one with the most benefit for school and community: an aquaponics unit."

Local businesses and tradesmen helped supply and fit the plumbing, equipment and electrics. The pool area is covered with a FlexiTunnel and needs little maintenance.

The unit operates as a closed loop system, where goldfish excrete waste into rainwater, which is siphoned through beds of either baked clay beads or scoria. Bacteria convert ammonia into nitrogen, which help the vegetables to grow. The plants in turn cleanse and oxygenate the water before it is returned to the fish below.

"We wanted to experiment with different growing media," Diana says. "Scoria is more solid, so provides good support for produce like tomatoes and beans. Clay beads move freely, so you'll get better shaped root vege. The unit has built up good nutrient levels and is sustaining itself. The longer it cycles the better the balance, and the better the growth in the beds."

The unit is mainly run by the students in Years 4-6 (aged 8-11), but it is used across the school curriculum. Pupils check water levels and test for pH, ammonia levels, nitrites and nitrates, and the temperature inside and outside the fish tanks – below-zero temperatures are common in Taupo. 

"The kids feed the fish every couple of days, they love seeing the fish poo and wee! Parents help at weekends, and we have a roster to cover summer and school holidays."

Any produce will be used in the school or local community. "I'm really looking forward to summer," says Diana. "Every day is a learning curve. I have no training in horticulture so if kids come to me and ask, 'How do we do this?' I say, "Let's go find out.' It's about them leading the project. When we do something we're all learning together."

- NZ Gardener

NZ Gardner