My favourite and most productive part of my garden: our small pond!

 

Jian Liu, from Camberwell, discusses her pond.

If you’ve never thought about growing edibles in a pond before, you should definitely give it a go! It’s easy and super productive. And it doesn’t even need much space. Think of it as a giant ‘self-watering’ pot which grows moisture-loving plants with no effort on your part, just place and forget.

I had never thought about having a pond before as part of a permaculture garden but I now think that it’s an essential part of our backyard ecosystem. With a few tweaks, we have managed to convert our green algae-filled pond, that has been a constant source of headache, into our favourite and most productive part of our garden – requiring no watering yet producing an abundance of food for us and nitrogen-rich materials for our compost, not to mention an absolute magnet for bees and beneficial insects! Sounds too good to be true?

A pond? But my garden’s not big enough!

You don’t need a big space at all to get the benefits from growing in water. Some people use a large flexi-tub that you can buy from the hardware store (or try hard rubbish), an old bathtub or wheelbarrow. When we moved in, we had a small existing pond around 2m x 2m square and about knee deep. It had around 10 goldfish, a water lily, and an underwater plant but, because of where it was positioned, it got lots of sunshine. The result? The water was always a green soupy mix filled with algae and we could barely see the fish, no matter how long we ran the fountain.

Our problem and journey to a solution

Our pond as it looks now.

We used to change the water a few times a year which was always a huge ordeal. It would look good for a month or so and then quickly turn green again, even quicker in summer. It was not only time-consuming, but completely ineffective and unsustainable.

I sought out advice from many pond stores and was told various conflicting things: “you have too many fish for your small space and an excess of nutrients; you need to get rid of some” (by this time the fish had grown to around 20+), “your pond is too sunny; the only fix is to buy a UV filter” (which not only was expensive, constantly wasting power, but would also kill off any good bacteria in the pond).

Most recently, we were sold some algae tablets – which were simple and inexpensive, just drop two into the pond a few times a year and it would fix all of our problems. Indeed it did, within a matter of weeks all the algae was gone and I have never seen our waters so crystal clear! It seemed like a magical and easy solution – however, not long after, our water lily and the water lettuce started to suffer. I tried to salvage them but some didn’t make it. It was a good thing that the fish were not harmed. But it was quite disheartening – like we were forced to choose between clean water and no plants, or plants but putrid green water.

Our solution

We now have crystal clear waters all year round. Azolla and water lettuce floating on the surface of the water.

I thought there had to be a better and sustainable way, without sacrificing fish or using chemicals. I researched – borrowed every book on the subject, joined forums online and did lots of reading. The only solution seemed to be to fill the pond with a diversity of plants (to suck up all the excess nutrients from the fish poo) and ensure at least 40% of the surface of the water was covered with plants (to prevent too much sunlight getting in and causing algae to grow).

We gradually increased the plants in our pond – divided up our single lily into 4 plants, planted many more plants (which I list below) and, most importantly, managed to source a large batch of azolla (which you can see covering the surface of our pond in the photos) – I think that this made the key difference. Since then, our water has remained clear without any intervention from us and, despite our expanding fish population of now 30+, I only run the fountain occasionally. As we are on a journey to transform our garden into an edible permaculture food forest, we have also added in a variety of edible plants into the pond to make the most of our space.

My top 5 benefits of having a pond/water feature

Bees using the azolla as a little platform to drink water on our hot summer days.

1. Insects love it – nothing in our garden attracts more bees than our pond. In summer, it is visited by a never-ending stream of bees, dragonflies and other insects. And growing surface plants help insects to drink from the pond without falling in.

2. It is the best place for growing many edible water plants (read below). They don’t need any watering. You can go on holiday and not worry about them, they grow like weeds as they have a constant source of water, no matter how hot our days are. Also, I suspect the fish poo is a source of fertiliser for them.

3. I’ve read (and it seems logical) that ponds help cool the garden in summer by releasing moisture which provides humidity for plants; while, in winter, ponds store up warmth which is released at night. So, the area around a pond becomes a micro-climate that many plants love.

4. It can provide a never-ending and sustainable source of materials for your compost and mulch (refer to section on azolla below).

5. Because water is pretty and relaxing! Water, fish and a fountain provide a visual focal point in the garden and create a wonderful place to sit beside and just watch the fish swimming around.

My top plants to have in a pond

Our small front yard water feature. Azolla turns pink when it gets lots of sun. Also note the yellow water lily flower.

1. Azolla – an absolutely essential pond and permaculture plant, particularly if you have goldfish. Azolla is a fast grower and consumes all the nutrients produced by the fish, thereby depriving algae of any food to grow. It also covers the surface of the water and prevents the sun from getting in (sunlight promotes algae growth). The recommendation is to have at least 40% of your pond surface covered by plants. In our sunny spot in summer, I usually aim for around 80-90% coverage. Azolla is a super fast grower and also has the benefit of fixing nitrogen from the atmosphere. I scoop out a net of azolla into the compost every few days and it’s an excellent compost activator or even mulch. And it is also a good fish and animal food!

Azolla can be a smart idea even if you don’t have any fish. Its common name is ‘mosquito fern’, which is a reference to the fact that, when it covers the surface of a water, mosquitos are unable to lay their eggs in the water. Anything that stops mosquitos in the garden is always going to be a favourite of mine! The azolla has single-handedly transformed our pond into an ecosystem: the azolla grows rapidly by drawing out the nutrients in the excess of fish poo we have -> we then add buckets of azolla to compost -> our compost feeds our fruit and veggie plants -> that in turn feed us.

As Bill Mollison once said: “you don’t have a snail problem, you have a duck-deficiency“. In our case, our problem wasn’t an overabundance of fish but a deficiency of azolla and other pond plants.

Vietnamese mint.

2. Other ornamental plants that provide surface coverage, such as water lily and water lettuce – these look pretty (nothing beats the glowing bring pops of colour of water lily) and relaxing as they float on the surface of the pond, but they also shield the pond from sunlight. Water lettuce grows so fast that it’s even outcompeted our azolla! I purchased one plant and, four months later had 30. They grow from little babies that break off and form their own families. Water lilies need to be divided up regularly: one plant will become four, then eight, and so on (you’ll have plenty to swap with others).

3. Edibles – there are water versions of many of the plants we like to eat. I think that these versions are easier to grow as they’re happy as long as there’s enough water in the pond – this whole summer, I only topped up our pond twice. (Tip: if your pond is too deep, sit your plants up on a few bricks, plastic tubs or whatever you have to provide a platform for the plants.)

Lebanese watercress (middle right), elephant ear (front), water lettuce (top left).
  • Mint – I have never being able to grow mint well in normal soil or pots. Either the soil is too low in organic matter or I just don’t water it enough. In the pond, it’s a different story – the mint grows with no effort. I successfully grow many varieties, including apple mint and peppermint. I also grow Vietnamese mint.
  • Watercress – as you might guess, watercress loves water. I’m growing two types: standard sandwich watercress and lebanese watercress (which has lovely fern like leaves). I’ve seen lebanese watercress marketed as ‘carrot plant’, as it does taste a lot like carrot, and it adds a wonderful pop of flavour to any salad or stir fry.
  • Water chestnut – this has been my first season growing these and they’ve really taken off! It looks like a pretty water reed and all you do is bury them into compost enriched soil, and plonk the pot into the pond and it grows and grows. It is said that each corn can produce over 200 corns, so I’m looking forward to lots of sweet water chestnuts for salads and stir fries. They also freeze well so they can be used all year round.
  • Water spinach – also known as ‘kang kong’ is used in stir fries in Asia. It only grows well in warm weather and I plan to give it a go in spring.
  • Water chestnuts planted in storage tubs found in hard rubbish, filled with soil and compost.
  • Water parsley and water celery – I haven’t tried these yet. Water celery looks pretty with variegated leaves, and apparently tastes like a mild version of normal celery.

4. Other ornamental marginal/bog plants – to create more height and texture in our pond, we’re also growing a number of ornamental bog plants around the edge, including water papyrus, water lily, flowering water iris and elephant’s ear.

5. Oxygenating plants – as their name suggests, these are plants that grow under the water to help provide oxygen to the fish. I’ve read that their ‘oxygenating-effect’ is overrated and that the fountain is more effective, but it doesn’t hurt and they provide a good hiding place and rich underwater ecosystem for the fish. We have elodea and ribbon plant (vallisneria), which are common and fast growers.

And there you have it – our water wonderland! I hope that reading about my journey inspires you to add a pond or water feature to your garden or, if you already have one, gives you some ideas about how to make it work for you.

If you’d like to follow us on our journey to create an edible permaculture food garden, you can find us at www.instagram.com/melbourne.foodforest, where I post regularly.

Water papyrus and water iris.
Elodea and water ribbon, normally growing under water but I pulled some up for this photo.

  10 Responses to “My favourite and most productive part of my garden: our small pond!”

  1. Hi Jian Liu
    Can you give us an idea of the size of your pond?
    Can your system be scaled up to convert a swimming pool for fish and plants?

    • It’s 2m x 2m square and around 60cm total depth, although the water is rarely filled up to the top. Yes, from what I’ve observed, if you are converting a swimming pool to a fish pond it’s absolutely essential to have lots of plants otherwise your pond will be green even with a pump and fountain. A friend of mine converted their swimming pool into a pond and I’m encouraging her to write an article about the process 🙂

  2. Thanks. Great article.

    I have a small fish pond with goldfish and am interested to try. May I know where to get the supply of the top plant i.e. edible and oxygenating plants?

    • Thanks George! You should definitely get some edible plants, especially with goldfish – their poo is a great fertiliser for water plants.

      Most nurseries, e.g. Bulleen Art and Garden, have a good supply of water plants, including edibles. Or you’re welcome to contact me I always have some for swapping.

  3. Great article – thanks.

  4. Are you using a pump or a filter to keep the pond oxygenated?

    • Yes, we have a pond fountain pump, as you may be able to see in the second photo – it has a large sponge under the water which acts as a filter.

      We rarely run it now since introducing all the plants – probably around 20 minutes per day (and only in off-peak solar times) – because we just don’t need it anymore to keep the pond clean. And also to save power, plus water lillies don’t like water being constantly splashed on the leaves. The plants do the cleaning and oxygenating.

      Before having the plants, we used to run it 10 hours+ a day and the water would still be green!

  5. Wow, Jian, very inspiring. Thanks so much for sharing all this info, I have a couple of ‘water holes’ I’ve set up around the place for the critters of the wild and I’m trying to grow some other type of weed on top of the water (round leaves) but it doesn’t grow faster than the goldfish can eat it. I’ve googled Azolla and it’s in fact a very amazing plant – any idea where I can get some from?

    Cheers
    Nadege

    • If they are small round leaves, I think you might be talking about duckweed. That’s another water surface cover similar to azolla, but doesn’t have the benefit of fixing nitrogen. It looks pretty though!

      With the plants that fish like to eat, you do need to start off with a substantial amount, otherwise it will all be gobbled up by the fish and disappear! And another a trick is to introduce any new plants just after you’ve fed the fish – then they won’t show too much interest in your new plant.

      I initially bought a small amount of azolla online and it basically all disappeared when I put it in the pond (the fish might have eaten it and/or it dispersed). It’s only when I got a much larger amount off someone locally that it really took off. You’re welcome to contact me if you like some azolla 🙂 otherwise have a look online for someone nearby.

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