Selecting a filter for your pond can be overwhelming. Skimmers, box filters, waterfall filters, upflow, gravity, pressurized, bead, mechanical, biological, in-pond, external, drum. And then comes all the different types of filter material. The filter system is one of the most important parts of your pond’s ecosystem so it is wise to select with care.
In fact, filter selections truly can be complicated. Not all ponds are created equal and not all pond owners are either. Not only do you want an adequate filter, but you also have to balance your filter budget with how much maintenance you are able or willing to do. If money is no object, you can install filter systems that are automated and virtually maintenance-free.
Many filter manufacturers will provide information on the pond volume that the filter can handle and it may be hard to know what to trust. Yet others don’t provide this information at all. Even when you have the pond size a specific filter is rated for there are many variables that can alter this; fish load, fish types, plant life, sunlight, fish food, and feeding routines all play a role. Some manufacturer’s will break this down and tell you the appropriate pond size with fish or without fish and this can help. If they don’t clarify that, it is best to assume they mean a pond with no fish.
These 5 steps will help you get started in the right direction with this important process.
- Determine the size of your pond. As mentioned, there is far more to it than just the size of the pond, but this is still a critical factor. Not sure how many gallons you have? See our article on 3 Ways to Calculate Pond Volume.
- Determine fish load. Average recommended fish load is about 1 goldfish for every 50 gallons or one koi for every 250 gallons. So let’s say you have a 500 gallon goldfish pond. This would be sized for about 10 goldfish. But if you have 20 goldfish, then you would be better served to look at a filter rated for at least 1000 gallons even though your pond is only 500.
- Factor in pump flow rate. This is especially important if you already have your pump or you know your waterfall needs a certain flow rate. Most filters will have a suggested flow rate or possibly a minimum and/or maximum flow rate. These ratings are provided for various reasons and it is important to follow the manufacturer’s guidance for best results.
- Determine the basic type of filter or combination of filters you intend to use. This is where we start choosing the basic layout.
If it is a small pond with few or no fish then you might choose to go only with a filter submerged in the pond. A large koi pond can get fairly complex. But most pond filtration systems will be somewhere in-between. See our page discussing the types of filters to help plan this step. This step requires a basic understanding of filtration. There are 2 primary types of filtration in a pond; mechanical and biological.
Mechanical filtration is what most people think of when they think of pond filtration, the physical removal of debris.
Biological filtration is providing surface area for beneficial bacteria to colonize on. This bacteria breaks down fish waste and other organics within the pond water.
Most ponds will feature a separate filter for each function with the mechanical filter being the first stage of filtration, such as with a skimmer. - Select specific filters. Now you know the basics you are looking for, such as you want a skimmer and a pressure filter. You are finally ready to choose exactly which filters to use. This is where you will rely on reviews, peer experience, expert guidance, and budget to select exactly which filters you will be using.
Proper filtration is one of the biggest keys to success in the pond keeping hobby. As such it warrants taking the time to make the best decisions possible to obtain and install the right filters for your water feature.