Goldfish, lettuce and the law: growing sustainably in Aotearoa

Overseas, aquaponics videos show people growing fish to eat. In New Zealand the rules are different, and they change how you design.

Which fish?

So most New Zealand systems are plant-first. The fish are the engine and the vegetables are the harvest. Leafy greens like lettuce, pak choy, silverbeet and herbs like basil grow best.

Never release

Koi carp probably arrived by accident with a shipment of goldfish in the 1960s. They now muddy lakes and rivers and destroy habitat for native fish. Never tip any aquarium fish, snail or plant into a stream or pond.

Cold winters and power cuts

In cool water the bacteria slow down, so many systems grow little in a Southland winter. Power cuts are the most common reason a whole system dies, because the pump, air and filtering all stop at once. Good designs plan for both: a battery air pump, fewer fish in winter, and someone on call.

No fish, no power: wicking beds

A wicking bed has a reservoir of water hidden under the soil. Water soaks upward to the roots, so less is lost to evaporation, and plants can survive a week or more without watering. That makes them handy for school holidays and dry summers.

Homes and marae as systems

The same thinking works for buildings. Rain on the roof can fill a tank. Kitchen scraps can feed worms that feed the garden. North-facing windows let in winter sun to warm the rooms. Each closed loop means less waste out and fewer resources in, which is one way of caring for the whenua and wai as kaitiaki.