Would be good in a non planted environment but too much aireation for a planted tank as the co2 would disperse too easily. The posher eheim externals have a wet/dry system.
The idea of wet/dry is that the exposure to air increases the oxygen supply and allows the bacteria to multiply faster. The average tank won't really benefit too much from this filtration wise since the bacteria colony is already built up, but it does help add o2 to the tank.
