Chemi-Mat is a revolutionary 12" x 12" phosphate filter pad for salt and fresh tanks. Simple and easy to use – just drop it into your tank, and it starts removing phosphates within 24 hours. After a total of 36-48 hours, simply remove the pad and throw it away. There's no physical breakdown of the pad and no phosphates released back into tank. Chemi-Mat contains no chemicals, does not affect pH and eliminates almost all PO4.