Pond construction


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Do it right the first time
I started koi keeping early in 1985, back then there were no filtration products to buy for a large koi pond. So I studied nature and learnt from her. Over the next few years I learnt some important things about building ponds, water management, filtration and koi health.
I will not go into too much detail here as most of the information you need can be found on this website.

When designing your pond...
Remember it must accommodate the growth of your koi. The filter must be capable to handle the extra load during summer.

Planning a large koi pond
Bottom drain it to settling tanks, pump the used water to the filter and let gravity do its job through the medium holding aerobic bacteria, a void underneath accommodates large perforated pipes returning cleaned water back to the pond via a waterfall. This is achieved by water displacement. The main point in constructing a koi pond is to get the plumbing right the first time!.

After two months planning, the layout of the proposed pond, settling tanks and filter:

The hard work
Nine months in construction. All hand dug and concreted by myself.

6 tonne of sandstone, 7 tonne of dirt and clay plus I needed a gofor for refreshments!

Note the reo spikes in the bottom slab to anchor the walls, pond floor thickness 20 cm at the shallow end and 25 cm at the deep end of high tensile reinforced concrete.

Pond walls were constructed by using string line only and within 5 mm of being level, all reinforced with 9.5 mm reo horizontally and vertically with high tensile concrete poured into the cavity of all bricks. All corners are rounded to aid water flow, 10 mm render allover, 3 bottom drains, one overflow pipe. Pond sealed with water based epoxy, 4 settling tanks to settle out solids, the large waterfall adds oxygen to the pond.

The hand cut sails ( 90% shade cloth ) are edged with seatbelt cloth on a home sewing machine with nylon thread, 550 eyelets in total around their perimeter for the stainless steel wire lacing, and heavier stainless wire supports the sails between the steel poles.

The finished job and koi
The pond is 6.8 m X 5.2 m, 80 cm deep at the waterfall and 1.5 m deep at the other end, it holds 46,000 L. Settling tanks are 4.8 m X average 1.2 m deep, it holds approx 5,000 L.

The filter is 3.2 m X 2.9 m, it holds 9,000 L.

In total the system is 60,000 L.

I have two Onga 400 watt pumps delivering 16,000 L per hour through 5 rotating arms to the filter, I also have another pump for a venturi to circulate and oxygenate the pond when needed.

If you are going to build a koi pond you must bottom drain, have a settling tank or tanks and a filtration system that is more than capable of doing the job. I CANNOT STRESS THIS ENOUGH.

This latest project was physical demanding, but was by far my most rewarding.

The more intricate something is the more prone to breakdown, so SIMPLIFY.

Article by 'Bottom Drain'