How Many Filter Brushes Do I Need?
Calculating the right number of filter brushes for your pond depends on two things: the size and shape of your filter chamber, and the diameter of brush you intend to use. Getting the quantity right ensures your filter medium is packed efficiently, with minimal gaps and maximum contact between the water and the brush filaments.
Use the guides below to find the correct number of brushes for your setup.
Rectangular Chambers
Rectangular chambers are the most common filter design and are well suited to all three of our brush sizes. We recommend using double interlocked spacing in rectangular chambers, where each row of brushes is offset from the rows either side to eliminate gaps and maximise filtration efficiency.
- 4 inch (10cm) brushes in rectangular chambers — includes a worked example for a 24 x 12 inch chamber
- 6 inch (15cm) brushes in rectangular chambers — includes a worked example for a 25 x 15 inch chamber
- 8 inch (20cm) brushes in rectangular chambers — includes a worked example for a 35 x 28 inch chamber
Circular Chambers
Circular chambers require careful attention to spacing to minimise gaps around the edges. Smaller diameter brushes pack together more efficiently in a circular space, which is why we recommend 4 inch or 6 inch brushes for circular chambers. 8 inch brushes are not well suited to circular chambers and are best avoided.
- 4 inch (10cm) brushes in circular chambers — recommended spacing at 3 inch intervals
- 6 inch (15cm) brushes in circular chambers — recommended spacing at 5 inch intervals
- 8 inch (20cm) brushes and circular chambers — find out why we recommend a different size
Not Sure Which Brush Size to Choose?
If you haven’t yet decided on a brush diameter, visit our brush sizes page for a full overview of the sizes we offer and guidance on which is best suited to different chamber designs. You may also find our layouts page useful before working out quantities, as the layout you choose will affect how many brushes you need.
If you are still unsure, get in touch with your chamber dimensions and we will be happy to advise.
Don’t forget: In circular chambers, brushes should be arranged so that there are as few gaps as possible round the edges. Alternatively you could use Black Knight vortex brushes