Changing Filter Questions.

Just hook it up and let it run, don't worry about overfiltration. As far as media I personally keep it simple and run floss/foam/polyfil whichever is around. Sometimes I use ceramic discs/lava rocks just for more places for bacteria to colonize also. Personally I run two large filters on my cichlid tanks and it seems to work very well.

well first of all what kind of cichlids are you planning on putting in the 55g?

on my 55g i have a fluval 304 and a biowheel pro 60 and the water isnt too bad for how overstocked it is. i also have this POS bravo 200 also that i had layin around. but i think you will be fine with the 2026 as it is rated for 100g tanks, i was gona buy that 1 but i didnt cause of $$$ issues. but i would leave the emperor 400 on the tank cause its never really bad to have too much filtration and it will help the ehiem out when the ehiem in new to the tank, IMO.

on media i would just use what comes with the ehiem or just use what it recommends i think it is 1 coarse and 2 fine filter pads, the carbon filter pads and the 1L efimech and 4L efisubstrat but if you are going to use the ceramic media you have you may want to use less of the efisubstrat depending on how much of the ceramic stuff you have.