Pond Water Filters

There are two basic kinds of pond water filters that are required in ponds.

Let me preface that by saying if you they require these filters IF you are using a pump. Natural ponds use plants as their filter systems.)

Filter What

We need to filter two things in our ponds.

The first is all the organic “crud” that is in the water. Think old leaves, floating debris, dead microorganisms. Without this organic material filter, this material simply floats around clouding the water or it sinks to the bottom of the pond to form a layer of rotting organic material. We want to remove this from our ponds.

The second water garden filters are used to adjust the chemical balance and bacterial imbalances of the water itself. Fish and plants change the chemical nature of the water and we need to keep this in balance. Natural ponds have natural ways of doing this but we have to use a mechanical device to create a biological filter.

Two Filters

So, we require two water garden filters - an organic material filter (like a pool skimmer) to clean the crud and a biological filter to balance the water and deal with bacteria.

Very tiny ponds will often use a system that combines both functions into a single unit that is married to a pump. If you use one of these, be aware that you need to follow the same rules of operation as the larger units if you want it to work. (clean out the organic material filter regularly, add bacteria to the pond, make sure the biological filter is cleaned once a year but no more).


So what happens if I don’t have both of these water garden filters? That depends on the load you create with plants, fish and water movement. If you have too many fish you create an excessive biological load, if you have too few plants you’ll create a biological load, if you have too much water movement you can create an excessive load because you're stirring up pond debris.

Combine any of those and you have a pond problem. Frankly, you’re likely to have trouble in your pond. You’ll wind up with algae (murky water) or unbalanced water chemistry (fish gasping at the surface constantly) and an entire range of other problems.

Wrong & Right

The guys in the garden center said I didn’t need these two filters. They’re wrong. Or, they’re right if they want to keep selling you loads of chemicals to fix all the problems you’re creating by having an unbalanced system. We’re talking water clarifiers, algae removal products etc etc. All these things are taken care of by the installation of proper filters. Having said that, if you don’t have problems now with your filters then the load on those filters is good. Do not add more fish, reduce plant populations etc to change that bio-load.


These are really expensive to buy. I guess it depends on your point of view. Yes, setting up a pond can be one of the more costly parts of your garden (definitely costs more than a pack of marigolds) but a well built pond adds to the value of your house and landscaping. Yes, you can write a large cheque to get a good pond but think of the enjoyment factor. A pond is a lot cheaper than a summer cottage! :-)

Home Built

Yeah, but can I build these water garden filters myself? Yes, you can. There are plans on the Internet for home built water garden filters. The question in my mind is whether you can build something as good as the pro’s make it (probably not) but is it good enough to do the job (depends on your skills).

One of the things that some gardeners like to do is tinker. If you are a tinkering kind of gardener, then sure you can put the water garden filter system together yourself. Follow the construction guidelines and you’ll be fine. As long as you understand you’ll be tinkering with the system instead of enjoying it. Remember that the pro systems use specially constructed plastics for their systems. These don’t degrade or crack in freezing conditions (freezing and water do very nasty things to plastic). If you use cheap bins, there's good news too. You’ll be replacing those box store plastic bins every few years and that will give you the opportunity to rebuild all that rockwork and dig up those plants.

If you purchase the heavy duty types of bins that will stand up (feed stores usually carry them) I suggest you do a bit of price comparison between the cost of the bin - the cost of the supplies to set up the filter and what it will cost you to purchase a specialty water garden filter. You’re going to find that the price differential isn’t all that high.

This holds true for things like the hoses you use. If you use cheap hose to carry water from the filter to the pump, you’re going to find it cracks and degrades (don’t freeze cheap hose with water in it). You really want to use high quality components (think spa grade rather than plumbing grade). Moving rocks and landscaping to repair a leaky hose is not something you want to do on a hot summer weekend (they always break down on summer weekends). :-)

I don’t have those in my pond right now, what do I do? That’s a “depends” kind of question. It depends on how big your pond is. Preformed plastic ponds can balance their water with plants - see algae control page. Bigger ponds with liners are looking at a rebuild. Or, a serious attempt at balancing things with plants and definitely keeping fish levels down below recommended levels.

The reality is that if your pond is not doing well right now, it has a problem. You can either fix the problem by installing it properly with the proper water garden filters or you can continue to complain and band-aid your pond.

Water garden filters are one foundation post of good pond performance.