Pond building seems like an addiction looking back. We regularly have periods of construction, but there were long periods, even of decades when we just enjoyed the ponds, did koi breeding, and took dips in them in the summer heat.
A while ago I wrote about the way we use biofiltration, fish and plants in a natural swimming pool system as part of our water saving strategy on a tight budget. I’ve also written about garden ponds in general and my ecosystemic design plans for our old pond.
First I will give you a little history of our pond building. Our first fish pond on the spot was a giant pvc sheet weighted down by water in a 1 metre deep v shaped hole. We’re built on at least 3m of sand, an old sand dune, and subsidence bedevilled this pond.
As an alternative we submerged a deep portapool into the ground close by and this also subsided, bulging the liner inward. So I built a circular brick retaining wall in the ground for the portapool. The pond became part of a four pond koi breeding system. All was well for decades, till tree roots ripped its base and the leaks just wouldn’t seal. Then all the above ground portapools but one were drained and packed up as the house was put on the market, but we found no buyer.
After that I decided to repair and improve the pond, because fish breeding, my husband’s passion, requires more than one pond. Then we had a terrible drought, which is still ongoing, and the need for more rainwater storage capacity became evident.
In this article you will see how we built up the circular brick retaining wall above ground and cast the bottom. Ponds level with the ground get more blown debris, so the above ground wall is for keeping it clean. The wall was plastered and I ordered a PVC industrial grade liner. After that my partner and I felt a concrete bottom was needed. It would stave off root penetration which wrecked the old pond that was in the ground.
So the team who have always worked together on our pond through its checkered history and shared Koi fish and general pisicine enthusiasm for a quarter century, got together to cast a base on the pond.
These are my husband Stephan Kloppert (Koi breeder, worm farmer and food author) and his old friend Marc Niehaus (Aquaponics systems expert, fish breeder and very expert builder). We are exceedingly grateful to Marc for sharing his skill.
installing bottom drain
cementing drain in place
If there are going to be fish in the pond, we’ve found a bottom drain is a must. We bought a large one which will lead under the ground to vertical 100 mm stand pipe. This is pipe whose lip is lower than the pond surface, into which another loose pipe is wedged so tight that water doesn’t leak out, ideally. The loose pipe can be pulled out and the water pressure then forces the water near the bottom drain out through the pipe in a rapid gush, flushing out sediment and settled fish feces. 100mm is needed to get enough pull to do and also to prevent blockages. This water is very nutrient rich.
First they stamped down the bottom, then cut a trench for the pipes and installed the bottom drain in a bed of wire mesh as reinforcing. The trench was filled with concrete mixed by hand. I calculated that over a meter cubed of concrete was needed to make a 15 cm slab and I had ordered a cube each of sand and stone. For the main floor of the pond they decided on hiring a concrete mixer.
On the day after setting the bottom drain the concrete mixer arrived and they placed more mesh all over the bottom of the pond, raised off the dirt with small brick pieces so that the concrete could get underneath and the wire would be embedded in the middle of the layer of concrete. Marc’s two son’s Ethan and Jayden were there too, admiring their dad’s handiwork and helping with water and other stuff.
Marc worked flat out until it was done, a long long day, and we carried buckets of stone and sand until our backs were breaking. It was very hard work for everyone concerned but what a beautiful job was done !
The pond must dry completely first before adding the liner, which has been in the store room for a while. A cement lip must still be added on top of the wall. Then the liner must be attached to the bottom drain and the pond carefully filled with water while getting the liner in place in its final position. Then the liner edge is stretched over the cement lip, rolled up and pinned to the wall with special nails. After this capping bricks will be added at right angles to the wall and the wall will be plastered level with the capping on the outside of the pond.
I’ve many other intentions for the whole water ecosystem in which the concrete water tank is a central element. But no more of that. Remaining a bit detached from the ideas that drive the project helps me with the patience that is required to see them realized.
To round off, a role model for planting, a picture of part of my sister's lovely pond system in southern California. Below you will find links to Marc Niehaus on facebook, where Marc posts pictures of his own aquaponic systems and natural swimming pool, and Stephan's website for comprehensive worm farming information.