What other types of Filters are there?
by: Demi Fortuna
Submersible Filters, Pressurized Filters and External Pond Filters all work both mechanically and biologically, separating solids out with varying degrees of efficiency, providing some form of substrate for beneficial bacteria to grow on and requiring various amounts of maintenance.
Submersible Filters are Prefilters, typically slotted boxes housing foam pads or poly mats, attached to the intake of submersible pumps, although some have built-in pumps. All work great to start with, since pads and mats are good particulate filters from the moment they are first submerged, but they clog relatively frequently, and must be cleaned right away, or the attached pump can starve for water, overheat and even burn out if neglected. Foam or poly, the media is somewhat difficult to clean, usually requiring a jet of water from the hose, and they never clean completely, and eventually need replacement. Their effectiveness as biological filters is tempered by the fact that cleaning them with chlorinated water kills whatever beneficial bacteria may have colonized the pads. They are cheap and effective but because they require messy cleaning or frequent replacement, they're usually used in small ponds as a first filter for new pondkeepers or for stay-at-home homeowners who can clean them as often as needed. Danner PM1000 Prefilters are a good example of this type. Pond Master Filters
External Pond Filters are versatile, easy to install, low maintenance filters that excel at both mechanical and biological filtration. The type that has become the industry standard is the Gravity Upflow Filter, so named for the direction water flows through it. Water enters at the bottom, is forced up through layers of media and overflows, clean and clear, out of a weir or port at the top of the filter and, by gravity, back down into the pond or stream. The layers of media not only filter out the finest particles, they provide plenty of surface area for beneficial bacterial colonies, which, constantly bathed in aerated water, continually remove ammonia and nitrites from the water column and purify the water. There's an External Filter for every size pond, but they are most useful in larger ponds, where their size and flow capacities easily handle even the largest applications. Properly sized, these filters are not only very effective, they are also very low maintenance. Large enough to retain the sediment of an entire season at a time, they can easily be plumbed to be backwashable, making end-of-season cleanouts that much easier. It's no wonder they have become the industry standard. See the Atlantic Water Gardens BF2600. Atlantic 2600 Filter Fall
Pressurized Filters - These filters are 'pressurized' because they are sealed units, part of the plumbing system. Because water is pumped into and out of them, they can be located near or far, above or below water level. That makes them extremely versatile, the ideal 'add-on' filter; all that's needed to install them is enough room to cut into the line coming out of the pump, usually without disturbing the rest of the line. Although the types of media inside them varies, Pressure Filters all work the same way; water pumped into them is forced through filter media then out of a plumbed discharge wherever desired. Many have built-in backwash valves to reverse the flow through the media and flush debris out of the filter. Since many ponds use low head, low pressure pumps, some filters use air or an agitator to stir up individual pieces of media and assist in clearing debris; these assisted backwash Pressure Filters are the least maintenance, most sophisticated and most costly pond filters in common use. Lifegard Tarpon 40
Other, less expensive pressure filters use a 'squeegee' or press to squeeze debris out of foam pads, although this is typically less effective. Filters that use foam pads usually have to be opened and disassembled to be fully cleaned. Pro Eco CPF-4000 Pressure Filter