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How to build your own pond filter system

build your own pond filter system

Our step by step guide shows you how to build your own pond filter system quickly and easily, with simple calculations for how much volume you need.

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It might be less work to simply buy and use a ready-made pond filter, but if you build and install it yourself, you can optimally respond to the special requirements of your pond. Besides, it’s just fun to get a better understanding of the delicate balance of the underwater world. So let’s go, we are happy to help you with concise instructions and a few tips on what to look out for when you want to build your own pond filter system step by step.

Correctly determine the filter volume

First, two key questions. First: How big is the pond, i.e. how much water does it hold? You can calculate that you need a rain barrel that holds around 300l for a pond with 5,000l. You need two tons for three times the volume of water. 30,000 and 50,000 liters are sufficiently filtered with 4 and 5 tons respectively.

Second question: do fish live in it or will some live in it in the long term? Depending on this, there are of course different filter systems because fish naturally produce more dirt. You should consider this if you are building a fish pond filter system, particularly if you are building a koi pond filter system.

We are now introducing you to the basic version, which consists of a filter chamber and is suitable for a small pond with a maximum of 5000 liters. Depending on the size of the pond, you can further expand the system according to this model.


  • Hole saw bit set for drilling the threaded holesTo the product


  • Pond pump
  • Pond hose 32mm diameter as a connection between the pump and the first filter chamber
  • UVC lamp (‘light pump’) to kill thread algae and other harmful green algae
  • Rain barrel (s) with a capacity of 300 lserves as a filter chamber
  • 200l of the filter mat medium coarseas a filtering material
  • 1 fine filter matas a filtering material
  • 2 connections with 50mm diameter. Connections between several filter chambers and drain into the pond
  • Pond hose 50mm diameter. For connecting the filter chamber/s

Build your own pond filter system: step by step

build your own pond filter system

Prepare the subsurface

First you have to look for a suitable place near the pond where the rain barrel or even several barrels can stand without disturbing you. The ground should be level and if you want to set up several tons, you have to create steps with a height difference of 12-20cm. Remember that wooden scaffolding is subject to greater wear and tear. It is therefore advisable to concrete the steps so that the amount of water is reliably carried.

Choose the right pump

The greater the difference in altitude, the better. However, your pump should have the appropriate performance. So check how deep the pump can be under water and calculate the size of the barrels or the steps in order to know beforehand whether the pump has the necessary power to pump the water to the appropriate height.3

Attach the ‘light pump’

You attach the hose with a diameter of 32mm to the pump. This leads to the UVC lamp ‘light pump’. It is responsible for ensuring that no thread algae can spread in your filter. Thread algae not only clog the hoses and make it difficult to clean the filter chambers, they also disrupt the bacterial balance in the filter chambers.

The perfect location of the water hoses

From the light filter, the hose continues to the first barrel (filter chamber). It should be long enough that it reaches just above the floor in the filter chamber , but does not hang too low to stir up the sludge below. This also applies to all other hoses. You should guide the water deep into the filter so that a complete water exchange takes place, but not lie on the floor and wash up the dirt.

The influence in the filter chamber

Put the bin (or bins) at their later destination. You can now drill the first hole in the lid of the first barrel. It should have a diameter of 32mm. Then carefully deburr the edges. Now attach the first connection piece and the hose that goes up from the pump to it.

The drain or water drainage

Now you drill two holes in the opposite side wall. They should each have a diameter of 50mm. They are also deburred, then you screw the hose connection tight. The hoses that you attach to it can either lead into another filter chamber or lead the water back into the pond. Further tons would have to be provided with two holes and connecting hoses. 50mm is a good measure so that the water flows off evenly and the barrels do not overflow.

Set the water supply correctly

You can also lay a stable pipe as a drain to your pond. However, this should have a slope of a few centimeters per meter. It is best for fish and the water parameters in general when the water splashes into the pond, because it drifts in oxygen, which is necessary for fish and plants.

To improve the water quality

The greater differences in height between the individual bins make sense, because the water “collects” enough oxygen through the rippling inside the filter or outside the pond. This is what the pond needs in order not to silt up and tip over or to be able to take care of its inhabitants.

You could also build a wooden panel if you don’t like the look of the bare bins that much. Equipped with a flap, something like this would be an elegant, discreet solution so as not to disturb the view of the pond.