I have a group of 12 tanks on racks (4x 30 breeders, 4x 40 breeders, 4x 50 breeders) the 30's are on the top shelf, 40's in middle, 50's on bottom.
I have matten filters in all 12 tanks, along with sponge filters, and HOB's on a few of the tanks.
I try semi religiously to do regular water...