When space is at a premium, it is cheaper to build up than out.  And so, the APS Vertical BioBed was born.  Now in use in many applications, it has proven to be effective and often is installed out of the way in unused space above a tank.  Due to the nature of the design, the weight of the BioBed is minimal compared to other biofilter styles where building above a tank may be cost-prohibitive due to structural requirements.