Fluidized Bed Filters

Fluidized bed filters are highly efficient, relatively inexpensive and require little maintenance when properly installed in a saltwater system.

Marine tanks, just like freshwater tanks, need effective filtration to remove waste from the aquarium water. There are three kinds of filtration which are normally present in one way or another in any aquarium system. They are:

This article discusses biological filtration and what many aquarists consider to be the most efficient biological filter—the fluidized bed filter.

While live rock in sufficient quantities and wet-dry trickle filters can serve as stand-alone biological filtration mechanisms—fluidized bed filters are significantly more efficient than any other biological filtration method. The reason for this is that biological filtration is all about surface area, and fluidized bed filters maximize the surface area of the bio-media by suspending (or “fluidizing”) the bio-media in system water.

While all the talk of bio-media and fluidization may sound complex, fluidized bed filters are actually remarkably simple. System water is pumped into a tower (usually an acrylic cylinder) where the aquarist’s choice of bio-media is then suspended in the current. The water is then forced out of the filter and back into the system.

In terms of bio-media for a fluidized bed filter, there are many choices, and most do a fine job. Again, keep two words in mind when choosing your bio-media for a fluidized bed filter: surface area. While spherical bio-media is good, there are those who say angular bio-media such as Lifegard’s Fluidized Bed Filter Media (which boasts 71 square feet of surface area per pound) is better. The bottom line is that any of the bio-media commonly sold for use in fluidized bed filters is going to be more efficient than the media in a wet-dry trickle filter.

Once the selected bio-media has been placed in the tower, water is pumped into the filter lifting the media into a fluidized state. Because the media is 1) always moving, 2) in constant contact with other media, and 3) perpetually wet, all surfaces of the media can be colonized by beneficial bacteria (unlike in a wet-dry trickle filter). These beneficial bacteria grow quickly in this environment and rapidly coat the media where they can absorb the ammonia and nitrite from the system water.

In terms of maintenance, fluidized bed filters are almost entirely self-cleaning given the fact that the bio-media is always colliding with other bio-media and hence knocking off debris. The only maintenance the aquarist must do is possibly to add media lost during normal operation. One warning: if there is a power loss, the fluidized bed filter can rapidly become toxic as the oxygen starved bacteria dies. Don’t allow a mature fluidized bed filter to remain off and connected to the system for more than an hour.

QuickSand and Pentair are generally the best reviewed fluidized bed filters available to the hobbyist. Of the two, Pentair’s is probably the best choice for the hobbyist. While QuickSand does make excellent fluidized bed filters for industrial use (they are often the choice of many large marine ornamental wholesalers and retailers), QuickSand’s smaller models lack the flexibility in plumbing that the comparable Pentair models possess. Pentair fluidized bed filters can be plumbed in several different configurations which makes them ideal for the hobbyist.

Highly efficient, relatively inexpensive and easy to maintain, a fluidized bed filter is an excellent addition to any marine system.


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