Rena FilStar XP Dual-density Microfilter pads are the final stage in the mechanical filtration of the aquarium with the Rena Filstar external filters. These will remove the smallest of particulate matter and are used to "polish' the water. These dual-layer pads will last twice as long as the standard micro-filter.
Each pad is two layers with coarse density fibers in one layer for trapping larger particles and a finer density which traps the smallest debris. This design allows the larger particles to be trapped in the first layer while the second layer traps the remaining finer particles. The benefit is that the bottom layer is able to trap more particles before saturation which reduces the frequency of cleaning and overall filter maintenance
