Indigenous Nursery News Blog

As promised in the Random Harvest Indigenous Plant Nursery Newsletter – this is the instructions for creating a small pond in your garden.

A picture is worth a thousand words, so click on the diagram below to get an idea of what you are seeking to achieve.

Placing the pond

1. Place the pond near a tree or fairly dense shrub where the birds can seek refuge
2. Position it so that you can relax and watch the comings and goings of the wildlife
3. Check in which direction the water would naturally flow and place the pond accordingly so that it looks as natural as possible.
4. Check for tree roots or other underground obstacles such as water pipes and electricity cables before using a pick.
5. If you have children make sure you will be able to secure the pond.
6. To attract wildlife place the pond in a quiet corner of the garden.
7. Make sure the pond has at least some strong direct sunlight.
8. Small ponds and water features need some form of circulation and filtration. You would therefore need an electrical point for your system.  

Digging the pond

1. Mark out your pond – this can be done with flour.
2. Remember the bare hole looks a lot bigger than when the pond is finished so add about 25% to the size of the hole
3. Make sure that about one third of the edge is very shallow and gently slopes in towards the middle of pond.  This is vitally important as it is the area the birds and insects will use and feel safe.  They will not use a pond with steeply sloping sides as they will not feel safe.
4. If you are creating a little waterfall (recommended as this helps aerate the water) make a ledge which will be covered by the liner and onto which you can place the base rocks of the waterfall.
5. Trim the edges neatly.
6. Place a thin layer (about 5cm) of river sand on the bottom of the pond, the ledges and edges.  This gives you a little leeway to seat the rock properly.
   You are now ready for the liner.

The liner

My recommendation is the Firestone Pondgard EPDM Liner.   Not only is it flexible and easy to lay and fold but is also 100% safe for aquatic life.

Remember to measure the hole accurately and allow ample liner to go over the edges.  If you buy only just enough liner to cover the hole, even the slightest movement could cause leaking over the edge.

Take particular note of the waterfall or “pot” area as these are the areas where the liner may move while working with it.  The water could leak behind the liner under the rocks.  This is very difficult to see and would mean breaking down the whole waterfall to fix it.

1. Line the hole with Bidim (Geo Fabric) making it as smooth as possible.  Make sure it overlaps over the edge of the pond.
2. Place the liner on top of the Bidim also making it as smooth as possible.
3. Smooth the liner out folding it carefully to take the shape of the hole.  Make sure it overlaps the edge of the pond so the rocks can be placed on top of it.  This holds and hides the liner.
4. Fill about half full with water.  This helps to ensure that the liner is seated properly before you place the rocks.
5. Place the rocks of your choice around the pond – the smoother round river stones are more in keeping with the theme.   Leave the shallow area clear.
6. Leave some cavities in between the rocks to create habitat for frogs and toads.
7. If you are making a waterfall place the rocks submerged on the ledge you made.  You could also lay a pot half filled with rocks on its side to pump the water through.   Both systems will help aerate the water.
8. Place the pump in the pond.
9. Cover the pump with ‘Leca’ biobags.  This is an inexpensive biofilter system for the pond.  You will need 1 biobag for 3m² of wall space (not surface area)
10. Hide the hose from the pump to the waterfall or pot in between the rocks as best you can.  Once your plants have grown a bit they will finish the job of hiding the pipe.
11. If placing a pot push the hose that is connected to the pump through the hole and seal it with silicone before it gets wet.  Remember you can always cut off a piece of pipe so rather push it through the hole more than is required to give you some leeway once the silicone has dried.
12. If making a waterfall you will have to use cement and building sand mix to grout between the rocks to prevent the water from flowing behind the rocks.  The proportion is 3 parts building sand to 1 part cement.

On the shallow edge place gravel to a level that some of the stones actually stick out of the water a little.  This will make it easy for insects to use the water.

This liner is available at Random Harvest – let us have your measurements and we will order it for you.

Preformed fibreglass or plastic pond 

1. Mark the size of the pond – using the actual pond as a pattern.
2. Dig the hole to a depth of the pond plus about 75mm.
3. Place a layer of riversand in the bottom of the hole to a depth that will allow the edges of the pond to be about 50mm above the level of the soil.
4. Put water into the pond to a depth of approx. 100mm – you will use this water to make sure the pond is level.
5. Jiggle the pond into the riversand at the bottom until the pond is level.  Make sure the edge does not go below the surrounding soil level.
6. Once you are happy that the pond is level start to compact the soil around the side

Pre-formed fibreglass or plastic ponds.  Once again place a thick layer of river sand in the bottom of the hole that is slightly larger than the pond.  Place the pond on top and fill with a little water.  The river sand makes it easy to move the pond around until the water in the pond shows that it is actually level.   Once level fill around the pond and compact well.

Water Quality and natural balance in a pond

If you wish to have a clean healthy pond it is important both to keep the water moving and to have a bio-filter. 

This need not be an expensive exercise although I do recommend that you buy the best quality pump you can afford.

There are many different bio-filters but they mostly work on the same system.  We use the inexpensive, easy to install and very effective ‘Leca’ bio-filter system of light weight expanded clay aggregate, in our pond.  This is the system we keep in stock in our nursery.

How does a bio-filter work?

Excess nutrients in the water caused by fish dung and decomposing plant material create perfect conditions for algae to proliferate and when this happens the water turns cloudy and unhealthy.  A bio-filter is the natural way to clean the water.

To create a bio-filter you need to provide habitat for bacteria that will digest all the excess nutrients in the water.  When the bacteria have colonized the bio-filter, the nutrient content is reduced.  The result is that the pond is clear and is no longer a suitable habitat for the proliferation of algae.  This is a completely natural system. 

When a bio-filter is newly installed it takes a little time for the bacteria to reach the numbers required to keep the pond clean, so a little patience should be exercised in the beginning as it may take up to a week for the water to start clearing.

For a bio-filter to work it is essential that there is adequate water circulating through it, ideally it should be the volume of the pond three times in 12 hours.

The bio-filter medium must have a surface area at least equal to the surface area of the pond structure (walls & floor).   As mentioned before we recommend the ‘Leca’ bio-filter bags.

Use 1 ‘Leca’ bio filter bag per 2500 litres of water.  The ‘Leca’ bio filtration bags are packed in shade netting around the pump which will draw the water through the medium where the bacteria will digest all the excess nutrients.

When you are finished building the pond you can now relax and watch the wildlife that will appreciate all your hard work.