Cheap alternative Bio Mechanical filtration - mmm Donuts!
So I was looking everywhere for plastic pot scrubbers to use as biological mechanical filtration but could not find them cheap or plentiful enough. But one day I stumbled into a preteen girl accessory store (claires or what have you) and discovered thing called "hair Donuts". They are dense layers of plastic mesh in wrapped in many layers, used for making hair buns. Ive found them in a ton of places and they seem to work excellent in my filters. Tons of surface area, I would say even more than pot scrubbers.