Depends on what kind of media you are using.
For me, canisters are mechanical filters, I don't use large media like carbon, phosphate sponge or ceramic for surface area.
For mechanical, they work best right before you clean them. So it's a trade off between working extra well and losing flow in your tank.
If you are using it as biological, it's best to have some kind of mechanical in front of it. Biological should be clean surface area for bacteria to grow, and not be forced to pull sediment out of the water.
For me, canisters are mechanical filters, I don't use large media like carbon, phosphate sponge or ceramic for surface area.
For mechanical, they work best right before you clean them. So it's a trade off between working extra well and losing flow in your tank.
If you are using it as biological, it's best to have some kind of mechanical in front of it. Biological should be clean surface area for bacteria to grow, and not be forced to pull sediment out of the water.