the garden pond as aquatic food garden and man made ecosystem

Enjoying the garden pond cum swimming pool cum fish pond in high summerThe cool waters of the garden pond - swimming pool - fish pond

Having a garden pond can become part of your lifestyle. 

With me its really my husband’s fault. First he raised guppies in a tank, then we bought some Koi and I built a small pond. Then he worked for a Koi breeder with a big farm and mud dams and was taught by a Japanese breeder who flew in to trouble shoot, and he started raising worms and continued to become a vermi culturist and backyard koi breeder. The positive result of all of this is that we’re not afraid of water systems and it helped pay off the bond.

setting up the aquaponic system and planting mintjust after planting the barrel
the mint plant in the aquaponic system a few months laterthe mint a few months later

Most recently we’ve ventured into aquaponics, and got as far as growing plants in the secondary filters, in plastic barrels. The mint is huge, the bullrushes were problematically enormous. I've learned from a friend who is continually experimenting with aquaponics. 

Easy aquaponics integrated with the garden pond

a simple koi pond in our gardenthe existing 'top' fish pond
natural bio filter for koi fishexisting natural bio filter

The above system is very low maintenance. You can see the two pipes coming from the biofilter back into the pond, and the pipe coming from the vegetation filter containing Cyperaceae.

With ease of management in mind, I have designed a new, expanded system and will start building soon. We used to have four tanks and this was better for managing fish breeding.

I wish to add a second pond, bio filter and vegetations beds to the present fishpond and bio filter, all driven by the same pump, and using gravity feed to get water from one tank to the other. We will than have two fishponds with a total capacity of about 15 cubic metres, plus two bio-filters each a cubic metre and a series of six growing tanks on an ebb and flow aquaponic system, driven by a small second pump on a timer.

For this ebb and flow action in the grow beds, bell siphons are ideal but they are just too sensitive to a multitude of factors and so hard to get right. You can make them out of throwaway plastic parts, but we’ve tried repeatedly without producing a reliable result, and so has our friend who is a mechanical and technical genius. Unfortunately we need to get on with the growing system using our power supply and hopefully one day we’ll build a predictable bell siphon.

The fish population in this aquaponic system will be low, whereas most aquaponic systems carry a high load of fish to provide enough N, but which makes them unstable, as a broken pump can mean massive fish death. We want a system that will not kill the fish if it breaks down while we are out for the night. This system will be a hybrid system. It will consist of a low fish population aquaponic system, a natural swimming pool and a fish pond with totally recyclable water, not requiring water replacement due to N buildup, all rolled into one.

Our future new-old garden pond

the old 'bottom' pond lined with brick and plasterthe old 'bottom' pond lined with brick and plaster

I intend using the shell of our old bottom pond, building it up, adding a second circular wall outside this, placing the grow-beds between the two walls and connecting everything in the grow-beds, backfilling with sand from the pond and then getting the connections ready to the top pond and the bio-filters, with valves on them perhaps. Once we’ve placed the bottom drain in the bottom pond (so called as it is lower and the final drainage point before pumping back up to the first bio-filter) I will line it with a custom made PVC liner, and we can seal the connections, connect it to the top pond, fill it with water and start the system.

barrels to make grow bedsbarrels to make grow beds
cubic tanks for filterempty cubic tank for filter
patient bricks await pond constructionbricks for pond construction
bottom pond contextbottom pond context

This is all good, but what it misses is the total aquatic eco system, with frogs, dragon flies and all the small creatures in such a system. This isn’t really possible without still water, and systems that support Koi fish require fast moving water for oxygen. 

rough sketch of bottom pond with grow beds, the second bio filter will stand next to the other bio filterrough sketch of bottom pond with grow beds, thanks to Marc

If the grow beds do not enrich our eco system sufficiently, I’m thinking of adding some kind of a side pond that completes the system in this way, a part that takes pond runoff, or even gray water, added slowly, and constantly, and does not feed back into the main system, as a stagnant pond will be a breeding ground for Koi pathogens. I would love to recycle our gray water, but the dirty soapy water will not be good for the Koi, so these two aspects still need careful thought in order to integrate them.

In the meantime I will overview some ponds I’ve photographed in the recent months. I love water gardens, so I can’t refrain from snapping one I like.

An unusually shaped well at the house of artist Irma SternA shapely water well at the Irma Stern art museum

The green walls above surround a well at the Irma Stern museum. It was the artist's house and she bequeathed it to the nation.

This garden pond makes clever use of shallow water and narrow channels to create a feeling of expansive reflective surfaces.shallow linear garden pond creates expansive reflections

This clever garden pond design is a long channel only two feet wide and two feet deep. Yet it creates a racetrack for the fish and a vast open space reflected in water, while its straight lines frame the view with patches of blue sky and direct our attention at the horizon.

Aponogeton distachyos, an edible native water plant grows in this lovely garden pondAponogeton distachyos, an edible native water plant grows in this lovely garden pond

Raised from the earth with retaining walls of unpainted but graciously bevelled concrete, this garden pond is also long and narrow. It is full of waterlilies, iris and white flowered Aponogeton distachyos surrounded by a mix of blue and white native and exotic flowers.

Cyperus papyrus growing in garden pond in San Diego California. The papyrus of Egyptian history, and its tubers are edible.Majestic Cyperus papyrus San Diego. Its tuber is edible.

I am busy researching what edible plants can be grown in the new system I'm planning, and there are many options, but as can be expected the quota or knowledge of edible aquatic native plants from South Africa is small.

Starting with native plants there is the water-uintjie or water ‘onion’ Aponogeton distachyos, which is available commercially in South Africa, and an element of traditional Cape cuisine. Its flower buds are best braised with aromatic Karoo mutton. Then there is the arum lily Zantedeschia aethiopica of which young leaves are eaten only when well cooked. Berula erecta is a medicinal herb for treating toothache, hence its Afrikaans name tandpynwortel (toothache root).

Plants from the same families as certain indigenous species are eaten elsewhere in the world and some experimentation and research will be needed to find out if the local varieties are also edible. Papyrus tubers (Cyperus), Nymphaea roots (water lilies), multiple parts of Phragmites and Typha (reeds).

What looks like Taro, flourishing in the stream behind Groot Constantia in Cape TownWhat looks like Taro, flourishing in a stream in Cape Town

Other plants are already naturalized weeds and a little exploration will reveal how useful they could be in a permacultural aquatic system. Colocasia esculentum (Taro) or a look alike seems to have invaded certain river systems in Cape Town. Its close relatives certainly grow here well, I will need to see if these are edible species and varieties.

Some types of cranberries like Vaccinium palustre can grow in water gardens.

There are various herbs which grow well in water, from England Salomus valerandi or Brook weed, Nasturtium officinale or Watercress, Pistia stratiotes or water lettuce, Lemna minor or Duckweed, Mentha aquatica or water mint, Mentha pulegium or Penny Royal, and from warmer regions Ipomoea aquatica or water spinach, Bacopra monniera, Aethionema cordifolia or Lebanese Cress, Polygonun odoratum or Vietnamese Mint, Oenanthe javanica or water parsley and Centella asiatica or Asian Pennywort can all be eaten, some as herbs and some as vegetables. The young shoots of Pontederia cordata or Pickerel Rush can be eaten and its seeds are also edible.

Some of these foods may be pushing the boundaries of what is edible but I would of course like to grow the classic marsh food, like the lotus Nelumbo nucifera, wild rice, Zizania latifolia, Taro (see above), and water chestnuts, although there is some confusion as to their identity.  Water chestnut is seemingly a polysemous word and used for the Taro as well as for Trapa natans and Eleocharis dulcis. Confusion reigns now but more research will reveal the identity and availability of these plants, as well as their suitability for growing in a garden pond of a few cubic metres. Trial with lots of error is the spirit of gardening. 

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