I have my trays filled with ceramic ring. I also have a W/D filter that is almost all Bio. I think I need some mechanical. What can I add to my canister and which trays would I put it in?
You could get a finer sponge, cut the old sponges in half and replace the bottom half with the finer sponge. You could also put filter floss in the bottom tray.
Fluval also has the polishing pad and recommends that you put it into the top tray.
All you need is the stock factory foam in the mechanical frame. If you are convinced that you need more mechanical filtration however in a 404/405 then cut up a replacement foam filter strip to fit in the LOWER basket. never put a polishing pad or other mechanical pads in the upper basket the way they show in the instructions. The flow is through the mechanical frame (top to bottom) and then UP through the baskets (bottom to top) You want your mechanical filtration to be continuious.
I run quite a number of 404/405 Fluvals this way and they work great.
I do have to question why your running all bio-media in the 405 when your also using a MUCH more efficiant (bio filtration wise...) WD. You don't gain any extra BB. You only have as much as the fish load can support...the rest is just dead space.
Understood. You can safely add up to two lower baskets worth of standard filter foam without reducing the flow to any great degree but avoid the temptation to run FINER mechanical media.