Fish Pond Filtration Media K1 Media provides the maximum active surface area for the bacteria to colonize, more than other types of static media. It is this process which removes harmful ammonia and nitrite from the water. How it is different to other media As the K1 Media moves within the filter, it causes the old dead bacteria on the outside to be displaced. This makes space for new younger heavier feeding bacteria to rapidly colonize. Within the wheel is a protected surface which enables colonies of bacteria to naturally follow their life cycle, of maturing, dying and then fueling the latter stages of the nitrification cycle