I tend to agree with the thoughts of media and I certainly prefer something that doesn't block. In reality I have a feeling that I may not even need biomedia in the 50g tank as it has a 2-3" depth of very course gravel/rocks (often 2" stones or so) and a lot of circulation with water running over and amongst this, so a lot of bacteria probably live happily there. Sure, I doubt it would be enough and I don't really want to risk the fish testing the theory...
Anyway, I also wanted a relatively compact above tank wet/dry, without a lot of blackage trouble, and stumbled over some relatively inexpensive chinese media that is fairly open (as per photo) that hasn't had any blockage trouble yet and should clean okay if it does. It's really just a ceramic sponge replacement...
The litre or two I have of this stuff is again probably overkill. I started with a third the amount and the tank was just fine, and in the end you really don't know where the bacteria are living. Well, actually you do - everywhere there's a solid(ish) surface - but you don't know for sure where the major numbers are.
I can wash the mechanic media (which sits above/before the biomedia) or replace it completely and nothing seems to change - tho you know for sure a large number of bacteria have to be living in the poly fibre mechanical filter as well...
I have avoided the real micro pore material so far due to the concerns with blockage and the doubt that I really needed the extra area. And I'm still thinking of maybe going with a bigger sump style system later on. At the moment the current filter is an experiment which, like many experiments on the tank, works so well there doesn't seem to be a lot of need to change it...
The good thing behind a biowheel is probably that the water just flows past and over it, rather than through it, so no blockage problem. They still have to have a fine structure to create the surface area and they would block quickly if the water had to trickle though the media. There are other ways this could be done, I bet, but it wouldn't look as cool as a wheel
