the media that comes with is pretty good. if you want better get some of that eheim substrate pro - little round ball things.
what size is the tank(s) they are on?
i just pour the water out, clean the sponges, rinse the carbon out, rinse the ammonia remover, do not rinse the media thing. and then i refill it with water.
connect it, and it runs perfectly. no need to prime or any of that rubbish - they work well.
my setup is:
ammo carb in the lowest, with a mesh of filter wool on that;
eheim media the next compartment,
a mix of that eheim stuff and the fluval stuff in the next, and
in the last - more eheim stuff :lol:
then i have another 405 with a different setup in it.
i clean mine every 3 weeks or so.... give or take.. depending on what mood im in. i only clean 1 at a time though. no time to clean both.
with me, the filter wool has never clogged the filter.
HTH