you can put filter media in.. it help remove and deal with specific issues... i.e carbon will help keep the water clear i fyou have water clarity issues... cloudy water, smelly water, etc...
the floss, willhelp catch food and poop, and chunks... i strongy urge that you clean and replace that filter often.. you cant replace it often enuf... as all it is doing is holding the poop and stuff in the water and constanty rinsing that back into the water, unless you remove it physically...
we really dont use terms like berlin... that is basically a remant from when we were learnging and tryied distinguishing the different types or methods...
basically, live and healthy rock, (hi amy), and as much flow and possible... and water changes as much as you can afford...
theat way is the best way, imho
gl
and yes, a 55 is a definate step up...