Running water in a garden can help to create the feeling of having your own little retreat, a place for contemplating and an escape from the everyday pressures of life. If well designed, fish ponds can also provide an interesting focal point and the kids will love feeding the fish. Water features are not hard to create and if you look around your garden there may already be the makings of a natural pond.
When Burke’s Backyard started preparing a garden for a makeover we discovered a beautiful natural rock shelf of Hawkesbury sandstone which had been overgrown with vegetation. Cleaning away the surrounding rubbish gave inspiration to creating a fish pond. Below the rock shelf a small retaining wall had been built and backfilled with soil. We removed all of the soil and added another layer of rocks to the retaining wall thereby creating a pond with an average depth of 30cm (1′).
We put a hose on the rock shelf to observe where the water ran and, after checking the levels with a spirit level, we decided to try something quite experimental. We thought that if we cut out a small pond in the rock shelf itself and pumped water into it from the pond below then the resulting cascade would look and sound spectacular.
Step 1 – Draw a chalk line to mark out the shape of the upper pond. Using a small angle grinder with a diamond blade cut out the edge. With a large angle grinder using a masonry blade cut parallel slashes across the rock to be excavated. Using a bolster and hammer break out the pieces of sandstone. Repeat this process about three times until the depth of the pond is 15cm (6″). Even out the surface with a small kango hammer. See diagram below.
Step 2 – Coat the whole area with Bondcrete to seal any cracks and to ensure that the slurry coat adheres.
The slurry coat is made up by combining the following:
Mix well and to three parts of this add one part of grey cement. Mix to a slurry and trowel around the excavated pond. Smooth off with a coarse sponge until the texture blends into the surrounding rock. To create colour throw minute amounts of red and green oxide, some brickies sand and some sieved blue metal dust onto the moist cement mix. Gently work in with the sponge until the colour of the pond blends with the surrounding rock. It may be necessary to add more of the reserved slurry coat to achieve the right colour. You can even paint in some lichen on the rock using a blend of pale green house paint, green oxide and blue metal dust.
Step 3 – Line the base of the excavated fish pond with 5cm (2″) of sand to ensure there are no sharp edges. Carefully position the butyl rubber liner in place ensuring that it is centred and that it comes up over the retaining wall.
Note: Before you purchase the liner it may be helpful to place a tarpaulin in the pond to work out the size of liner needed. Allow an extra 20% because it is better to have it too large than too small.
The liner will need folding in places in order to contour into the shape of the pond. Trim the liner along the retaining wall using a Stanley knife and cement the top capping stone into place. Cover the base of the liner with washed large round river pebbles then carefully fill the pond with water. Now you can trim the rest of the liner such that it is several inches above the top water level. Using rocks and logs camouflage the side of the liner. Take great care to avoid puncturing the liner. Large and small pebbles can be added around the edges for a final look. A few aquatic plants and ferns can also be added to soften the edges. We used Stream Lily (Orthothylax glaberrima), Maiden-hair Fern (Adiantum sp.),a miniature Arum Lily (Zantedeschia aethiopica) and a dwarf Papyrus (Cyperus papyrus ‘Nana’).
Step 4 – Install a submersible pump with a plastic return line running up to the rock pond above. We chose a 24 volt pond pump to ensure electrical safety. Be sure to purchase one which is designed to handle your lift (the height you wish to pump the water) and the volume of water you desire. An irrigation specialist will assist you with this. These pumps are designed to run constantly and they use the same amount of power as a light bulb. It is necessary to clean the filter regularly.
Note: Because of the cement work involved and the lime which leaches out of it the pH of the water could be excessively high for a week or two. Alum or aluminium sulphate (obtainable from chemists) can be added at the rate of 2 tablespoons per 100 litres of water. This can lower the pH and help to precipitate out the lime and any suspended clay particles, thereby clearing the water. After that, drain the pond by syphoning through your garden hose ensuring that you also siphon off the settled lime. Replace with fresh water and using a Burke’s Backyard pH Kit check that the pH is in the range of 7.2 – 7.6 (ideal range for most goldfish). You can add vinegar in small amounts to get it right if the pH is too high. Before you add expensive fish it may be best to test the water for several days with cheap goldfish.