Under gravel filter?

[dogofwar]

Pre-filters are essential for cansisters. Otherwise, they're pretty much just full of crud until they clog or slow (when most people clean them). Which is a PITA. I don't have any.

A deep bed undergravel filter is an enormous amount of media. Many times more volume and mass than multiple canister filters.

Poret sponge if used properly creates denitrification so more complex than simple nitrosomas and nitribacter.

Each and all different filtration methods have their own aspects to provide us flexibility and advantages.

I've got a couple of canister filters well prefiltered so not much dirt enters. Only cleaned when the outflow starts to reduce. I haven't needed to clean them for at least 9 years. Mechanical problems seem to occur when canisters are cleaned.

 

[dogofwar]

I like coarse Poret for that reason - really easy to clean.

Since all filtration basically does the same thing, by sucking detritus into the media to get it out of the water column, and into the media where aerobes convert ammonia and nitrite to nitrate, its kind of a horse a piece.
An UG filter pulls detritus into the substrate, same as a canister pulls it into the media in the can, or HOB pulls it into the box, and nitrate is spewed back into the tank.
The only real mitigation factor is how often the media is cleaned.
If you clean one more often than the other, that's the only essential difference.
The Under gravel filter collects detritus in the substrate, and if the substrates regularly cleaned by vacuuming it may be better than a infrequently cleaned canister.
I started fish keeping about the time the UG (then called the "miracle filter") was new, and becoming popuar, so I used it for many years.
I now use Porrett foam in my sumps, but calling it better is a stretch, I use convenience as my judgement of what's a better tool.
If I clean one more than the other, because its easier to do maintenance on, that's better.
To clean an UG filter properly, the substrate must be frequently vacuumed, to keep it from becoming a nitrate "sink", and in some way that frequent vacuuming may be better because it forces one to do water changes, the only convenient way to control nitrate.