The 3 Kinds of Pond Filters

I wish to stand corrected on one of my earlier posts regarding biological filters - it's been a few years since I had my last pond, and available products have vastly improved since then! The lava rock I recommended (since it provides a lot of surface area for the nitrifying bateria) has been replaced by bead filters which are far easier to clean.

So - I figured I'd take a few minutes to go over the different types of filtration, and the purpose for each. First, it is recommended that you have a bottom drain at the lowest point in your pond. This enables waste material to be drawn out, and caught in the first filter. This is a mechanical filter which traps large and small particles - fish waste, uneaten food, plant particles and so on.

You might also have some form of chemical filtration. This removes pesticides, colors, odors, and organics which were too small to be trapped by a mechanical filter.

Finally, there is biological filtration. This provides some form of medium on which the beneficial bacteria can grow - bacteria which convert toxins such as ammonia and nitrites into less toxic nitrates. Nitrates are in turn used as a food source by aquatic plants. However you set up your biological filter, it needs to provide oxygenated water, as these bacteria work best with plenty of oxygen.

For garden pond owners, if you don't have fish you may do well with just a biological filter. However, I still recommend installing a bottom drain, as you may very well need to drain your pond for cleaning, or to repair a leak. For fish owners, the removal of fish wastes and uneaten food helps reduce the buildup of ammonia, and will significantly reduce the amount of time you have to spend maintaining the water quality of your pond!