I've been doing a lot of rummaging around here and elsewhere trying to sort wheat from chaff when it comes to the FX5. The filter seems to have no real weakspots other than 1) a relative lack of track record (only about 5 years so far), and 2) less bio media capacity when compared to the Eheim 2260/62 or Pro 3 2080. Critics point out that the volume of the three trays in the FX5 is roughly equivalent to the (total) capacity of a 2217. The FX5's foam perimeter is noted as providing better mechanical filtration, but in comparing the bio-filtration only the inner baskets get considered. Is there a reason for this? Sponge is an excellent bio media so I don't understand why that considerable amount of foam isn't taken into account when the FX5's bio-filtration capacity is being discussed.