I am way over-stocked, and the pond is small, so I clean the skippy a
lot. The Fluidized I built by myself (also built the skippy as well)
Maybe 150 to 200 for the whole system (without pump).

I find fluidized beds to be quite cool. If you made one yourself,
I can only assume that you are well aware you need to reseed the filter
with a bacterial culture if the filter is off for 30+ minutes or so for
any reason, yes?

The bacterial colony in a fluidized bed dies practically immediately
if the device stops. The same is not true for many other filter media,
as the gaps between the media hold oxygen bearing water which keep the
bacteria alive for more manageable times.

All that said, fluidized beds are spectacularly efficient at what they
do. Is there any filter as efficient for the size? Don't believe so...

C//