This time last year O'Callaghan reveals she was so "fed-up with the effort to maintain her chlorine pool" she converted it into a giant fish pond. Yes, a fish pond!

Although some of her friends were "horrified at the thought", for O'Callaghan, who confesses she "has always loved ponds", the decision to convert her standard suburban 1.5 metre deep, and 8-metre long pool into a natural habitat was a no-brainer.

"In Canberra you spend a fortune looking after a pool and because our summers are so short you get so little use out of them, especially if like me, the kids and grand-kids have left town," explains O'Callaghan who now has more than 40 colourful goldfish swimming in her unwanted pool.

"But it's not just about the fish, it's also about the plants and the other wildlife," says O'Callaghan who reveals her pond has attracted a range of frogs, insects and birds.

"Last summer there were also heaps of dragon flies; red ones, blue ones, all lovely to watch," she explains, adding, "and I've just added a couple of decoy ducks which I hope will attract the real thing."

Earlier this week, my excursion to admire O'Callaghan's innovative oasis coincided with a visit by Lea Maddocks, a biologist who specialises in fish and aquatic environments and who has been providing advice to O'Callaghan in what both refer to as "a big experiment".

"I was so excited to have this job, as I've seen it done in the tropics and in Sydney, but never before in a temperate area like Canberra," reveals the gum-boot clad fish whisperer, as she gently entices another large gold fish from a bucket into the pond.

"This fella was getting a bit big for its old home at a private aquarium in Gungahlin, so I'm relocating it here where it's got plenty of room to swim around," says Maddocks who explains that it's the cold of a Canberra winter that provides the biggest challenge for the long-term survival of pond life.

"We lost some of the bigger fish this winter," reveals Maddocks, explaining "they came from pet shops and sadly weren't pond-tough, indeed all the smaller ones that were born in the pond survived as they had acclimatised."

To help the fish endure the harsh winter, O'Callaghan installed two large underwater heaters in one corner of the pool. Really! "It seemed to work as we found some of the larger fish regularly hanging out in the warm zone," explains Maddocks, adding, "hopefully next winter they will be a little more acclimatised and won't even need the heater."

But near-freezing water isn't the only life-threatening hazard for the fish. O'Callaghan says she "has become an expert in shooing away several hungry birds", including a cormorant she has nicknamed Cuthbert.

"When I first saw Cuthbert underwater taking my fish, I nearly died, I almost dived in after him," she reveals, adding, on one occasion he took a fish that was too big for him to handle, "which I rescued by shooing him away."

In response to Cuthbert's regular raids on her pet fish (each one which also has a name), O'Callaghan has installed a mirror on the fence so she can see the roof of her house from her study for "it's up there on the roof that he surveys the water before choosing his prey".

Getting plants to stay alive in winter has also been hard work, says O'Callaghan, pointing to the water-lillies planted in a submerged tower of old milk crates that are only now bouncing back with the warmer weather.

Despite these drawbacks O'Callaghan, whose study overlooks the pond, firmly believes "the conversion has been more than worth it".

"I'm writing a book so am in my study almost all day, it's such a peaceful setting to look out onto," says O'Callaghan, adding "it's very relaxing watching fish."

Maddocks agrees. "They buzz about like a big screen saver, plus you've got the added bonus of not having to feed them over summer," she says, explaining "they'll munch on a lot of the algae and biofilm that will grow around the pool gutter.

"It's still a bit of an experiment as to just how much you need to circulate the water with the pump and how often to backwash, but we are getting there, and in doing so creating a natural habitat for wildlife to enjoy."

When I first heard of O'Callaghan's pool conversion I had my reservations but having seen it with my own eyes, it's a novel solution to an unwanted pool, and much more fun that simply filling it in. It's also eco-friendly, cost-effective and promotes biodiversity. In fact, I can't wait to return in a year or two to see how much the plants have grown. Hopefully by then with more plant cover for the fish to hide amongst, Cuthbert and friends will have turned to alternative locations elsewhere to fill their tummies.

Pool conversions: Do you know of any other Canberrans who have taken the plunge to convert their unwanted backyard pool into a fish pond? If so, O'Callaghan would love to know.

More than goldfish: According to Lea Maddocks, chief fish whisperer at Belconnen-based Acumen Aquatics and Vivaria, you could also stock pool-sized ponds in Canberra with native fish including Blue-eyes, trout, and even barramundi.

Is it reversible? Yes, according to Maddocks all that is required to turn a fish pond back to a pool is to shock the water with a super chlorination.

Canberra myth? In the early 1990s, I heard a story about a number of Canberra pool owners who each winter stocked their backyard swimming pools with trout. According to the story, at the start of spring the pool owners would invite friends over for a fishing party to see who could catch the most trout; before returning the pool to more conventional purposes for the summer. On each version of the story I heard, the pool owner was invariably "a friend of friend" making the story difficult to verify. Is it an urban legend?