I have a 10g planted tank, and use a simple Whisper 10 HOB filter. My question is, the "Bio Bag" filtration media has gotten quite dirty and i've noticed sediments in the water column. I assume i need to put a new Bio Bag in but would this not remove alot of my biological filtration? I figured this may be a problem when i set up the tank so i did throw in a bit of eheim substrate pro into the bottom of the filter when i set up the tank so i do plan on just leaving that in there. How do most of you replace the filters in these and still retain a good amount of your benificial bacteria? thanks.