Potted water gardens, an update

Late last year I somehow managed to talk myself into starting up a little potted water garden, and the good news is that it's all progressing pretty well, but I've learned a few lessons along the way, of course, as all newbies do. And that's what this little blog posting is all about.

The peaceful scene this morning. Of the four original goldfish – John, Paul, George and Ringo – three have survived (Ringo, alas, didn't survive a scorching 40°C day fairly early on in the piece). The plants have grown like crazy, and I have learned that potted water gardens are a lot of work. I don't mind the work at all, but that's the main lesson learned. To keep the water clean, you have to both top it up and replace it very regularly.

At first I thought the Louisiana iris wouldn't make it, as the leaves flopped over and showed some signs of yellowing, but to my surprise the main stem has popped up a sturdy, dark green new bunch of erect leaves, and for good measure a second healthy stem has emerged. So I presume it suffered a bit of transplant shock when I repotted it, but now likes the manure-rich soil in which it's growing.

The other planting, a native floating fern called nardoo, is thriving to the point that I have to cut it back weekly to stop it taking over the whole pond. I love this delicate looking monster. This one plant in a six-inch pot could easily cover a water surface three or four times as big as my puny pond.

If you look closely at this shot you can see the underwater roots of the nardoo looking to spread out and take over the world. The goldfish also love the nardoo, as it gives them a great hiding spot to dart to the moment they sense any movement above the water.

The main issue with the pond is maintaining water quality, and as I don't have a pump with a filter (no space to fit one in) I have adopted a simple program of replacing about one-third of all the water roughly every 10 days.

To do this, I first fill a bucket with tap water and sit that out in the sun all day, to 'burn off' any chlorine present in the water (goldfish are said to be susceptible to chlorine, say all the experts). Then in the late afternoon or early evening, I let the water in the bucket cool fully, and use it to replace the pond water. I use a small 500ml plastic measuring jug to remove the water bit by bit, and once the water level is down by about a third, I wipe any green slime off the side of the iris's pot, as well as the pond pot itself. Then I replace the water using the bucket water. This has all become an easy routine, but it is essential maintenance.

During the hot weather of summer, however, the pond's water level sinks an inch or so each day, and so I just top that up with ordinary tap water without worrying about burning off the chlorine in the sun, etc. Adding one litre of tapwater at a time doesn't seem to bother the goldfish at all.

When I was in the supermarket buying the small plastic measuring jug that I use to gently add or remove water from the pond, I also picked up a cheap tea strainer, and this has proved a useful little 'scoop' to clean any bits of flotsam and jetsam from the water.

The reason for all this fiddly maintenance is sunshine. To stay healthy, goldfish need about half of the water surface to be bathed in sunshine, and the other half covered in something cool, protective and green (like the nardoo). When the sunshine hits the water, algae forms. If the whole of the water surface was covered in plant life, there'd be little or no algae, as algae needs sunshine to grow. But as I wanted goldfish (to eat any mosquito larvae) I had to accept algae as part of the deal.

Another serious promoter of algae is me. Well, to be more specific, the problem is me overfeeding the fish. These 'Comet' goldfish are really cute when you sprinkle the goldfish food over the water, going into a very greedy and entertaining feeding frenzy. And so early on I overfed them. Cheap thrills. Then I discovered the 'food block'. This is the white thing you can see in the pond. It's shaped like a seashell, and it's like a slow-release goldfish food. It's a much better way to feed them (great if you go away on holidays of course), and it also contains a few slow-release elements which help to clear up the water quality. Since I've started to use the food block, the water quality has improved and it doesn't need quite as much maintenance as early on.

And finally, the pond has given Pammy a whole new class of ornamental creatures to shop for. This is her latest purchase from our Darwin holiday, a cute little turtle that sits at the base of our pond.

And so the main thing I have learned is that if you take on a potted water garden you've taken on a fair bit of extra work – they're not low-maintenance by any means. I'm loving the whole experience so I'd encourage anyone interested to give it a go. I'm thinking of swapping over to a much bigger pot at some stage in the future, just to give the nardoo a more natural looking wide, shallowish pond of water to float on, but that's about the only change I have in mind at this stage. I guess when I get around to doing that, another update might be in order.