PO4 pad (phosphate-absorbing filter pad)

Product Overview

A PO4 pad (phosphate-absorbing filter pad) is a chemically infused aquarium media designed to extract excess orthophosphate (PO₄³⁻) from water to starve out nuisance algae and clear up your tank.

How They Work

Chemical absorption: The polyfiber material is infused with specialized phosphate-binding particles (often iron oxide or aluminum-based compounds) that trap PO₄ molecules as water flows through.
Mechanical backup: They double as a fine mechanical filter, trapping free-floating debris, uneaten fish food, and organic waste before it can decay.

Standard Usage Instructions

Custom sizing: Buy a standard sheets (like 10" × 18") and cut it down with scissors to fit your specific canister filter, hang-on-back filter, or sump compartment.
Placement: Place the pad after your mechanical foam but before your biological media. This keeps the pad from clogging with heavy sludge so it can focus on chemical absorption.
Strict replacement cycle: You must replace the pad every 4 to 6 weeks. Once the microscopic binding sites are completely saturated, the pad cannot hold more waste and can begin releasing trapped phosphates back into your aquarium.