The water flows from the bottom of the cascade canister filter up through each filter tray. Cascade 1000 has 3 media baskets.
The bottom basket is for FilterFirst Dual density filter pad with the soft side facing down. This pad will trap free-floating particles.
The middle basket will house your polishing pad (soft side facing down) on the bottom of the tray. The carbon pad goes in the same tray on top of the polishing pad.
The top basket will house your bio rings or biological filter media. We want the water to be clean of most debris before reaching the bio rings.