Indeed
Tested with all my media in place, which is (bottom up):
Tray 1: 2 filter foams and ceramic rings
Tray 2: ceramic rings and some bioballs
Tray 3: bioballs
Tray 4: 4 filter foams
2.5 litres in 10 seconds = 900L per hour.
Which means for my Rio 240 (which, once you've allowed for substrate and wood is about 195L) has 4.6x turnover.
If I were to transfer this filter to my new Rio 180 (which I imagine would lose a similar volume with substrate/hardscape, so I'm guestimating at about 140L) it would have 6.4x turnover.
Obviously this is hardly reliable as I only did it the once (due to an unfortunate incident with the hose coming off and spraying water all over the wall/floor, plus suddenly acquiring 4 extra children in my house), but it would be interesting for other members with the same filter or with the smaller filters to do similar tests on each so we can get actual turnover rates... if we were to do that I reckon it would require a dedicated thread in the Hardware Section... what do people think?
Personally, even if the turnover is not what it claims to be, I really like the size of it and the amount of media I can fit in there (even if the bioballs are infuriating!). I think in terms of biological filtration it's great, even if the turnover is not what's required for a heavily planted tank. But then I can add powerheads if I really want to increase the flow. If I had little to no plant mass in there then there's no reason why it wouldn't be sufficient IMO.