Choosing the Right Pond Filter: What to Consider

Summer is here, the shape of your new pond has been dug out and the liner is in place. It’s pond season and you can already hear the gentle trickle, picturing yourself sat beside your new pond in the sun watching the fish…But there’s that business with the pond filter… which one? There’s no perfect answer as every pond is different, but here are the main things you need to be thinking about when setting up filtration on a standard pond with no waterfall or fountain:

Set Yourself a Budget

There’s not much use in browsing around the hundreds of pond filters available until you have worked out how much you have to spend on the pond. Your filtration system is one of the most important features of your pond, so if you are going to cut any corners in setting your pond up, we don’t recommend you cut them here.

Working out what level of filtration you need

This is perhaps the most important factor in choosing a filter. Here’s how you do it: Step 1: Work out the volume of your pond. For roughly square, rectangular or circular ponds you can do this by using this formula:

Length x Width x Depth = Volume


3m x 2.5m x 0.6m = 4.5mᶟ

4.5mᶟ = 4500 Litres

  Step 2: Now we are really getting somewhere. We know the volume of your pond, and for the purposes of demonstration we will use this 4,500L as our example pond. Now you need to think about what you want in your pond. If you are keeping normal fish (eg, Goldfish) you need to double the hypothetical volume of your pond. This is because the amount of waste in the pond is doubled by the fish, meaning there is more for the filter to deal with.

Normal Fish: Volume x 2 = Filter Size required – MINIMUM

Example: 4500L x 2 = 9000L filter required – MINIMUM

This is fine for normal fish, however if you are going to keep Koi then we need to quadruple this figure. This is because Koi produce a huge amount of waste and your filtration system needs to work four-times as hard to keep up:

Koi: Volume x 4 = Minimum Filter Size Required

Example: 4500L x 4 = 18,000L Minimum Filter Size Required

Now we have our true figure and we can choose a pond filter that can handle that volume of water. It’s best to pick a filter that matches the volume as exactly as possible, but sometimes that isn’t possible. For our 18,000L example pond, we would select a 20,000L filter, but first we need to think about pumps and UV.

Pond Pumps

When it comes to pump fed filters, you need to select a matching pump that will feed your filter with the amount of water it needs to run at optimum capacity: Most filters state their maximum flow rate in terms of litre’s per hour and matching that is the best way forward. This means that you can treat all the water in your pond roughly every hour, meaning your pond will be as clear as possible. If your filter is going to be much higher than the pond’s surface then you may want to consider a bigger pump to help with the ‘lift’ required in pushing the water higher against the force of gravity. Choosing a pump that’s too large for your filter may mean there might not be much water left in your pond: instead it will be overflowing from the filter-box and lost to the earth.

UV Filters

Some pond filters come with a built in UV Filter Clarifier appropriate to the size of the filter, and some don’t. You need to decide if you want one included or whether you will buy a separate ‘In Line’ UV running into the main filter box. UV Filters comprise of a fluorescent tube emitting Ultra Violet light that forces algae to clump together, making it easy for the sponges in your filter to catch them as the flow past, cleaning your water.


For a safe and efficient pond, you need to look at the electrics involved. Choose a place for your pond that means you can lay the cable needed to run the filter and pump, and you may want to consider a Switchbox to run the electrics through, making them safer.

Got a little pond?

If you pond is particularly small, you can skip all this and get an ‘all in one’ type filter-pump. These are pumps that act as fountains or run small waterfalls that suck in the water through a built in filter and push it out vertically and they are quite handy for smaller ponds.

Other things

The advice given in this article so far has concerned normal filter and pump setup on an average pond. If you are thinking about anything more complicated then that’s great and whatever you’re planning it can be achieved more easily than you might think: You can set up waterfalls, fountains, bottom drain filters and lots more but you will need to read up on their slightly different setup. Stay tuned over the coming weeks for blogs on these great pond topics too!


  • Avatar eric thorpe Posted 08/07/2014 at 3:56 pm | Permalink | Reply

    advice needed please,
    Hi I am on your mailing list having purchased products before . I have 4 Koi + a sturgeon they are 12-15 yrs.old so very large now,my pond is only about 700gls. my system consists of Hoselock Easyclear 6000,+Hoselock Cyprio filter box.
    Easyclear needs cleaning every week
    cyprio needs cleaning every 3 third week
    No good ?
    thought about a easyclear 9000 but don’t think it will solve my problems.
    Could you please recommend a system within a reasonable price.
    Thanking you

  • Avatar Nicole Martin Posted 20/04/2016 at 11:42 am | Permalink | Reply

    Stop winter results for pond. Pondpro2000 particular liners are for security and supply water, atmosphere and warmth resistance. These liners empower upgrade at standard basis.

  • Avatar Steve Beesley Posted 23/07/2017 at 4:35 pm | Permalink | Reply

    Nice and helpful feature, thanks,

  • Avatar M\rk Cornish Posted 07/01/2020 at 7:13 pm | Permalink | Reply

    I intend creating a new pond in the next few months and was considering the Pontec Multiclear Set 5000 witch meets my needs, except ideally my filter and pump shoulds be solar powered. CAN you recommend a product with a similar spec except that it is solar powered\ Is there an issue with the biological filter with a solar power source – with bacteria dying if/ when the power fails?

    • Avatar Jeremy Gay Posted 14/01/2020 at 1:21 pm | Permalink

      The Pontec Pondosolar 1600 set would offer a similar flow to the 1500lph pump supplied with the Multiclear Set, but a filter needs power 24 hours per day, 365 days per year, in order to keep the beneficial bacteria alive.The Multiclear Set is also a pump, filter and UV, whereas the Pondosolar is just a fountain pump, for decorative and ornamental purposes. If you want properly filtered water you’ll still need to connect to the mains.

  • Avatar Antony Braddon Posted 29/03/2020 at 4:38 pm | Permalink | Reply

    Hi there I’ve just dug out a 3300m x2100m x900m fish pond can you help me with the size of pump and filter system I want to put in a natural waterfall, could you advise me on what to buy, I will be putting koi fish, many thanks tony

    • Avatar Jeremy Gay Posted 31/03/2020 at 10:13 am | Permalink

      Hi your pond has a volume of 6237 litres. If you need to power a waterfall and keep koi I would opt for a pump and filtration package for ponds up to 12,000 litres (double,). To power a waterfall the pump will need to be 6000lph or more.

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