On some of my tanks.. (the larger 50 gallon and up tanks) have aqua clears on them, or some sort HOB filter. The 180 does have a canister filter on it as well.
The large 1500 gallon koi tank is a sand/gravel DIY filter.
As for the others.. I run them from a meadow piston pump on sponge filters- and NOT the crappy hydor sponge filters.
For water changes, we have the 1500 plumbed into the piping. Then we have another part plumbed into the piping where we can just put the syphon in it, and it drains... and for most of the tanks, we have a 5 gallon bucket that was modified with clear tubing out the side that drains right into the sump.
I refuse to run sumps, or run filtration through multiple tanks because of cross contamination. This way if 1 tank gets something, it's only that tank that gets it.
The fish room may soon be getting an overhaul though... the outdoor pond will soon be done, so the indoor 1500 can either be used to house some tropicals... or I can take it down, and build a large ray tank. My only issue is I have to find a way to heat the basement before winter comes, or I am gonna be screwed on a lot of my tanks because I do not want to run heaters on every tank.