What does Prefiltration refer to?

by: Demi Fortuna

Pond filtration can be separated into two very broad categories, by when debris is taken out of the water column (before or after passing through a pump), as well as by how material is removed (mechanically versus biologically). Prefiltration refers to the removal of solids before they pass through the pump and get into the water column. Skimmers fall into this category because floating debris like leaves aren't really in the water yet; they are sitting on the surface of the water, giving the Skimmer a chance to trap them before they can sink.

More traditional types of prefilters include the screens and baskets on the pumps themselves, and the submerged boxes with mats or pads inside attached to pump intakes.

Regardless of the type of prefiltration, all provide two major benefits for the pondkeeper:

1. They make life easier; it's always easier to take fewer, bigger pieces of junk out than lots of tiny particles that have been ground up by the pump that will have to be mucked out later.
2. They keep pumps alive longer; it's always better for the operation and longevity of the pump to have a good prefilter, since clogged pump intakes are the number one cause of pump failure, and the constant passage of debris wears down impellers.

Obviously, if the prefilter is full or clogged it can't clean the pond or keep the pump happy, so the longer you can go between cleanings, the better for the pump and the less maintenance for you. Look for lots of surface area and a way for clean water to get to the pump even if the prefilter needs cleaning, just in case you can't get to it on time. One great way to accomplish this is to use brushes instead of nets or pads in the Skimmer, since they get pushed to the side when full of debris and always allow water to get to the pump. Another is to use filter media that are very hard to clog, such as Matala mats, to go longer between cleanings without damaging pumps.