3 Main Types of Pond Filters

A man-made koi pond or water garden needs a filter to keep it clean and healthy for fish and plants. Here are the 3 main types of pond filters:

​Submersible Pond Filters

Submersible pond filters are the most basic type of filtration system. They consist of a flow-through box that holds foam or woven filter pads.

Some have a submersible pump that fits inside the filter box. It draws water through the filter pads. The filtered water then travels to the fountain.

All you have to do is submerge the filter box in the pond and it will start collecting waste materials (once you plug it in).

Submersible filters are easy to set up and there’s no plumbing work involved. The only drawback is that you need to remove the filter box from the pond and disassemble it to clean or replace filter pads.

External Gravity-return Pond Filters

External gravity-return pond filters are usually plastic boxes that contain foam filter pads. They collect suspended debris. Water flows into the box via a pond pump and then the filtered water flows out the box.

The filter box sits above the water so that water can easily flow back into the pond. These types of pond filters can be convenient but it may not be easy finding a space to keep the filter itself out of sight.

Pressurized Pond Filters

Pressurized pond filters draw in water through pumps. The water then passes through the filter media and returns to the pond. All this happens under pressure. These filters can be set up outside the pond or below the water level.

Pressurized filters reduce the water pump’s flow rate by about 40%. Thus, it’s best to over-size the water pump when using a pressurized filter system. Luckily, most manufacturers recommend specific pumps for their filtration system.