Patrick is referring to fluidized bed filters. They are a bit different, and as he points out they are a biological filtration. They are available for aquarium systems, and they were a big fad a couple of years ago.
Fluidized bed filters have two major disadvantages. First, unlike a trickle filter, they are a closed device. This makes them major consumers of oxygen. A trickle filter has the bio media, and a thin film of water is run over it. This allows excellent gas exchange, and there is not a problem with the oxygen consumed by the bacteria. In a fluidized bed filter, this gas exchange doesn't exist, so the bacteria consume oxygen from the water.
Second, and this is the main reason why you should never even consider a fluidized bed filter, is that if the water flow stops for any length of time, the bacteria on the filter sand will consume all the available oxygen, suffocate, and die. A power failure of only an hour or two can cause this. You have instantly lost your biological filtration, which is the most critical part of any filtration system.
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