Swimming pool to billabong
  • Last updated:
  • 09 Feb 2021

Article and images by Dr Julie O'Connor, Senior Conservation Partnerships Officer

Have you fallen out of love with your swimming pool? Most of us know someone who has a backyard pool that they rarely use. If that person is you, why not convert your time-consuming, chemical and money hungry pool into a beautiful low maintenance pond? It’s easier than you think and the results can be breathtaking.

For your first step, if you have a chlorine pool just stop adding chlorine. If you have a salt chlorinator, just keep running your filter until it has used up all the salt. Most chlorinators have an “add more salt” indicator light that tells you when the salt in the water has been depleted. You will soon notice that in the absence of chlorine, your pool water will turn a spectacular shade of green. For once, in the life of your pool, this is a good thing.

Arguably the two most common questions that come to mind when contemplating a pool to pond conversion are the issues of water quality and mosquitoes.

Will the pool water become stagnant?

As anyone with a pool will attest to, you can become so used to expecting crystal clear sterile water that anything less becomes a cause for concern. Put those concerns aside and let’s have a look at how nature produces beautiful healthy water bodies. Aquatic plants are the key to great water quality. They filter excess nutrients and deliver oxygen into the water, which is vital for overall ecosystem health. The following are just a few of the aquatic plants that will bring health and beauty to your pond.

  • Blue Hyacinth (Monochoria cyanea) – not to be confused with the introduced and invasive water hyacinth, this sprawling herbaceous water plant produces little mauve to blue flowers. They produce many seeds loved by waterbirds as well as providing shelter for fish, frogs and invertebrates.
  • Water snowflake (Nymphoides indica) – another beautiful little native with leaves similar to the waterlilies and a delicate little fringed daisy- like flower. The snowflake also provides great shelter for frogs and fish.
  • Native hyssop (Bacopa monnieri) – a delicate sprawling plant with small edible leaves. It grows well in wet sand or mulch around the pond edges and makes a pretty addition around rocks and edges.
  • Tassel sedge (Carex fascicularis) – a beautiful erect sedge growing to 1m. Great for planting into a floating reed bed.
  • Nardoo (Marsilia mutica or M. drummondie) - a perennial aquatic native fern with floating leaves that resemble a four-leaf clover. Nardoo has long been used as a food plant by indigenous Australians.
  • Yellow bladderwort (Uttricularia australis) - an unusual plant that floats vertically submerged in the water column and produces a single exquisite yellow flower that protrudes above the pond surface. This plant brings the added benefit of growing its own insect traps that take wrigglers out of the water.
  • Duckweed (Lemna minor) – a tiny floating plant that has the capacity to double its surface area in only a few days in high nutrient conditions. Some people don’t like duckweed for that very reason. However, if you don’t mind netting it out of your pond it does have some benefits. It is eaten by a variety of animals including, not surprisingly, ducks. In parts of South East Asia people also eat dried duckweed for its high protein content. Also, like most aquatic plants, being high in nitrogen it makes great compost for your garden. Just keep in mind that if left unchecked it can cover the water surface and prevent light from reaching the bottom of the pond.

All the wetland plants have their own preference for where they live in a pond. Some will tolerate frequent submersion, others will happily live completely immersed and some others prefer the damp edges with only occasional inundation. A good native wetland plant nursery will be able to advise you about growth requirements for a range of plant species.

You may like to even include your own private island. A floating reed bed planted with, say, Carex fascicularis will make a beautiful and functional addition to your pond. An internet search will bring up a variety of commercial suppliers or instructions for making your own.

What about mosquitoes?

Second only to water quality is the concern people have about potentially providing a breeding haven for mosquitoes. Generally temporary pools of shallow water provide the best opportunities for mosquito breeding. So your well-planted deep swimming pool will not only have a depth not favoured by mosquitoes, but it will also have a host of fish and invertebrates that will make short work of any occasional wriggler.

In south east Queensland, the fish listed below are excellent native choices that will flourish and control any mosquitoes in your pool.

  • Aggassiz’s perchlet (Olive perchlet) (Ambassi agassizi)
  • Australian smelt (Retropinna semoni)
  • Bug-eyed goby (Redigobius bikolanus)
  • Duboulay’s rainbow fish (Melanotaenia duboulayi)
  • Empire gudgeon (Hypseleotris compressa)
  • Firetail gudgeon (H. galii)
  • Fly-specked hardyhead (Craterocephalus stercusmuscarum fulvus)
  • Marjorie’s hardyhead (C. marjoriae)
  • Ornate rainbowfish (Rhadinocentrus ornatus)
  • Pacific blue-eye (Pseudomugil signifer)
  • Purple-spotted gudgeon (Mogurnda adspersa)

One part of the pool to keep an eye on in relation to mosquitoes is the skimmer box. If the water level stays above the skimmer box you won’t have a problem because your fish, frogs and invertebrates will still have access. However, if the skimmer box water is isolated from the rest of the pool, just be aware of the potential for mosquitoes to breed in that shallow water. One way to ensure the water level in your pool stays high enough is the installation of a water diversion hose from your downpipe that diverts water to your pool whenever it rains. Keep in mind though that a more stable water level will also influence your choice of plants, possibly changing conditions for those that prefer only periodic inundation.

I first wrote about my pool conversion in 2013, so seven years later do I have any regrets? Not a single one. In addition to providing habitat for a wide range of invertebrates, reptiles, amphibians and birds, it has given me some great wildlife viewing opportunities right in my own backyard.

So, if that once loved pool in your backyard is losing its appeal, consider creating your own beautiful oasis. You will be decreasing your ecological footprint and increasing the biodiversity in your own backyard.