Canister filters???
How they work, water is siphoned down into the bottom of the filter then goes through the media and is pumped back onto the tank. So your media should go, (bottom to top) sponge, biological, then finally a fine mechanical like wool to keep the water crystal clear.
Here's a curly one, just cleaned out my filter and found old Java moss all through the biological media meaning the moss somehow made it past the sponges or there is some black magic going on inside that filter.
How they work, water is siphoned down into the bottom of the filter then goes through the media and is pumped back onto the tank. So your media should go, (bottom to top) sponge, biological, then finally a fine mechanical like wool to keep the water crystal clear.
Here's a curly one, just cleaned out my filter and found old Java moss all through the biological media meaning the moss somehow made it past the sponges or there is some black magic going on inside that filter.