Sydney Pond in subtropical garden

Our pond in Sydney's northern beaches! Temperate zone with sub-tropical summers.


When we moved into our house 2 years ago now the backyard was just knee high weeds. About 1.5 years ago I started on the garden and pond.

First photos are of the weed pit that it was when we arrived. There was a piled sandstone rock retaining wall holding the upper level, but that was all.

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This second set of images are the build process for the main pond. This was in January 2021. I put in some garden beds down the lower level, then started on the pond on the edge of the top level retaining wall.

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This third set of photos show the initial build finished and the start of the bog plant out. The bog is 30% of the surface area.

The pond is mostly 30cm (1 foot) deep because any deeper and you need to fence it off here in Oz and I didn't want to have to put a fence in. There is a small section that's 40cm deep for a fish cave but that's only a very small bit of the pond.

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By February 2022, even though the bog was planted out well and the plants in there were going gangbusters I was still getting a lot of string algae. I think the combination of the sun and the huge amount of leaves that fall into it from the surrounding bush has meant a LOT of nutrients in the pond. So I decided to add a second much deeper bog in a big garden bed-like box, hoping that a ton more surface area for bacteria and room for deeper plant roots will knock off some of the nutrients. Then I built a little river coming into the main pond with a bridge. The top bog empties into a big pot (to contain splashes and reduce water loss), which then empties into the little river.

By this time I've also built a chessboard patio and pergola up the back (with giant chess pieces, woohoo), and the top of the yard is planted out with beds and paths.

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These final shots are now, October 2022, which here in Oz is Springtime. Everything is going berserk in the garden, and the pond looks reasonably well established after only 1.5 years. Though we are about to replant the lawn section on the lower level because the last lot of turf we put in all died (we walked on it too much, oops).

The pond has heaps of tiny native fish, which are breeding like crazy. I have no idea how many are in there. It could be anywhere from 50 to 250. I really have no idea. Everywhere you look they are swimming about. I tried to photograph some but they're too small and blend into the ground too well. I don't even remember what species they are. I know some are Rainbow Fish but I can't remember the others. I made sure they are all non-invasive species and then chucked about 30 in last year. Whoever survived winter and bred are who is in there now. They seem happy.

Some of the fish are mental adrenaline junkies and swim up the river, jumping out of the water onto the rocks and then flipping over and over out of the water until they finally flop into the upper ponds. That was a popular sport when the river was first put in, but has become less so as some of the idiots died on the rocks when they didn't make it. I suspect they were teenage boys.... Darwinism in a microcosm.

I only put very small frog friendly natives in, so the frogs and tadpoles are happy. We get frogs bopping away all night in the pond, and there are regularly huge half-frog tadpoles about in the bottom. Around the rocks we get mats of frog spawn. A family of Kookaburras moved in last summer and has stayed all year, I suspect eating the frogs and some fish. Many other birds come in for a swim most days, including Sulphur Crested Cockatoos (a colony lives in our massive 200ft tree above the pond), Magpies, Rainbow Lorikeets, and King Parrots. We also get big water dragon lizards sunbaking on the rocks and dragonflies all over the pond in spring/summer.

I am having a lot of trouble with string and mat algae in the pond this spring. I assume because of the enormous amount of leaf matter and the bright sun on the pond all day. But I'm hoping that when the plants in the top bog really get going that will get better. I'm also hoping that some of the big tropical plants get taller they will give some shade. Fingers crossed. Otherwise I'll have to work out a way to add another bog.

It's 100% natural bog filtered (as advised by the masters here), and the levels in the pond seem to be pretty good. I'm at 7.2-7.4 PH. Ammonia, Nitrate, and Nitrite are all testing at 0. The water is crystal clear at all times. The only issue is the string and mat algae. That can get pretty bad, especially down one end. I'm in there about every 3-4 weeks pulling a couple of buckets of the stuff out at the moment. I really hope that improves, it's very annoying.

It's all still a work in progress out there, so excuse some of the mess. A couple more years and things should be much more settled and established. I've still got to finish off the bridge section and build a bridge to match the patio, this one's only temporary. And also need to finish off the top of the bog box when it works itself out more. But it's coming along.

The dream is to put a freshwater bog filtered swimming billabong in there.... one day, one day.

I'd like to take this opportunity to thank everyone here at the forums who gave such great advice when I was starting this 1.5 years ago. Particular shoutout to addy1, GWBUDD, CW, poconojoe, and brokensword. Thanks!

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