Potting up a water garden

Three weeks ago I had no intention of setting up a potted water garden. And now I have one. Sometimes things work out that way – everything firmly out of control here in my little patch.

My neighbour across the road, Gino, is moving house, and he came to my door three weeks ago and offered me a set of four nice, empty, blue-glazed pots at bargain prices. I already owned a couple of pots in the identical shape and glaze, so the deal was easily done. The largest pot in the set had no hole in the bottom, and that's where this whole potted water garden thing got started. It's the obvious thing to do with such a pot. It has taken three weeks to figure it all out to my satisfaction, and if you're interested in a marathon 19-photo blog entry on how to set up a water garden in a pot, written by a complete newbie to the art, this is what lies ahead on this page. If it's not your thing, I understand completely.

OK, let's begin at the end. Here it is, photo taken half an hour ago. All set up. Tall thing at the back is a Louisiana iris (it will have deep blue flowers one of these days) while the greenery in front comprises two plants: nardoo, a native floating fern, and azolla, an aquatic weed (I'll explain later). Though you can't see them, goldfish are in residence, to eat the mozzie larvae as well as being pets (sort of).

Rewind three weeks. The large glazed pot with no hole in the base. Thank you Gino.

The plants, each ten bucks at Bunnings. Louisiana iris left, nardoo right. As it's not a large pot, I thought that two plants would be all it could take, but the azolla was recommended to me today, and so I bought some.

The nardoo (Marsilea drummondii) is a native floating fern from our inland watwerways. It sits in a pot with the pot about an inch or so completely underwater. The leaves look like four-leaf clovers and it'll spread to cover the water, probably a bit too much for the fish's liking. So I'll occasionally cut it back. It's a popular water plant here not only because it looks nice but also because it's easy for newbies like me to grow.

This is Pot-a-Seal. It's a spray-on internal pot sealant that's recommended for terracotta and other porous surfaces. If a ceramic glaze has no flaws you don't need to spray your pot with it. But I figure that Gino bought his pots from the same 'Pots Seconds' shop nearby where I bought my blue-glazed pots, and I suspect they're seconds because of some kind of fault, perhaps in the glaze. After spraying the inside of the pot with this stuff, it dries in an hour, then you can fill the pot with water, so it's a good precaution to take.

Here's a handy tip. Make sure the pot is level before filling it with water. It looks so much nicer when the water is the same distance from the rim on all sides.

As a test run I set up the nardoo and iris still in the plastic pots they came in from the shop. The top of the iris pot needs to be out of the water (say, one-third out, two-thirds immersed). The nardoo is completely submerged. It took about a day for the nardoo to tidy itself up and spread out nicely, so don't worry if it looks a bit ordinary on day one.

The trouble with the temporary arrangements is that they looked terrible. Nardoo on a house brick, the iris on a brick and then some pavers to get to the right height. A much better set up was needed.

Then, to reinforce the point about a better set-up being needed, two days later we had a day of torrential rain which turned the iris into a wreck. OK, lesson number two learned: windy days were going to be a problem for tall plants in light plastic pots.

And here's the solution. A tall glazed pot (again from Bunnings, just $10) that sits inside the water pot, with its rim an inch and a half out of the water. My plan is to fill the bottom four or so inches of the water pot with pebbles to hold the tall iris pot securely. And that meant repotting the iris...

Thank goodness for Google! It seems that watery irises such as Louisiana irises and Japanese irises love acid soils. The ideal potting mix for them is a 50:50 blend of acid garden soil and well-rotted cow manure (apparently the most acid of the farmyard manures). Garden soil is needed as it holds together well in a pot in water. Potting mix is hopeless, apparently. My garden soil is acid, too acid in fact (I'm working on it), but at around pH 5.5 it's ideal for irises. So making up the potting mix was very easy – I only needed half a shovel full of soil to do the job.

I already had a bag of cow poo on hand, as I use it in my garden on my vegies and as a light mulch to gently feed various potted plants. It is a wonderful plant food. The procedure for potting up the iris was to fill the bottom of the pot with several inches of pebbles (I used a layer of large pebbles in the bottom, topped with a layer of finer gravel, the same stuff you can see on the top of the potted-up iris a couple of pix earlier). Then I added several inches of the soil/manure mix on top of the gravel, planted the iris rhizome into this, and topped all that with an inch and a bit of more fine gravel (which stops the soil mix floating away).

Around the base of the iris pot I decided that black pebbles would add a sense of depth to the look of the water pot, and so this is what lines the bottom four inches of the pot.

I removed a fair bit of the water from the pot to get the iris pot secure, then topped up the water after that. (By the way, from my Googling I've learned that watery iris such as the Louisiana and Japanese iris are really plants of the water's edge, not for growing underwater. They prefer the rhizome (ie, root) not to be underwater all the time, but they can cope with the odd flooding episode without any bother. And so that's why you should aim to have the rhizome sitting above the waterline.)

Once I topped up the water I then had to wait a week or so to let the water settle down, before adding the goldfish. This step is important, because tap water contains traces of chlorine, which can kill the fish, but if you sit the water in sunshine for a few days the chlorine 'burns off' and disappears. And so, this morning...

Four Comets, $2.50 each from Marrickville Aquarium shop. The goldfish aren't just there to be pretty. To earn their keep, they will be eating mosquito larvae. Not all goldfish are suitable for water pots outdoors, but Comets are, and so are Koi carp. Everyone recommended Comets to me, and a great tip was not to waste money on buying big ones. As a newbie, my first attempt at goldfish may or may not work, so at $2.50 a pop the price is right.

Here's an important step in releasing goldfish into a water pot or pond. Leave them in the bag of water in which you brought them home from the shop. Open the bag to let in oxygen, then place the whole bag still holding the fish, in the pond water. Leave it there for about 20 minutes, during which time the bag water will slowly become the same temperature as the pond water. Apparently goldfish can handle very cold water and also very hot days, but they cannot cope with sudden changes in their water temperature. So ease them slowly into their new home is the kind way to settle them in.

After all that, as soon as they were released they went straight to the bottom and did nothing. Oh no! But five minutes later they had got over the shock of being in a watery world with black pebbles on the bottom and plants on top, and they were exploring their new home.

Apart from feeding the fish, my job is to control the spread of the water plants so only half of it is covered with greenery. The goldfish need access to the surface. However, they really appreciate the cover provided by the plants, giving them somewhere to hide when cats and birds spot them. As the pot is over 30cm deep, that depth of water adds to their sense of security. At this stage I thought that was it, but with more Googling and phoning I decided that the goldfish needed some kind of natural food plant to supplement the mozzie larvae and the goldfish flakes, and so...

...I bought some azolla. It's an aquatic weed, but there are several species of azolla, and my water garden shop assured me this is not the one on the banned list (the really bad one has yellow flowers, this one doesn't). This plant has roots attached, doesn't need potting and just sits and spreads on the water surface. Its presence will oxygenate the water, which is good for the goldfish, and also handy at keeping algae away from the pot – and the fish like to eat it, too. Its downside is that it spreads easily, but getting rid of it is as easy as scooping it out by hand. And as I will be regularly feeding the goldish I can't see it getting out of hand as I am a bit of a neato, or so I hear. The main thing when getting rid of the excess is to add it to the compost heap, where it soon dies when away from the soaking water it needs. The alternative is the garbage bin, and the crucial thing is of course to keep it away from drains.

And so to repeat my opening shot, here we are this afternoon with the new water garden on the go.

I'm happy with how it looks, but I am sure that in a month or so an update will be worthwhile in confirming where I went wrong, or did OK. Are the goldfish still alive? Has the azolla taken over? Are we being eaten by mozzies? Are the plants still alive, for that matter. I had never thought water gardens could be so exciting, but thanks to Gino this might be the start of something big!