Alternative to filter wool?

[Ingwe]

Hi guys,

I am using an IOUS tank with a media compartment which has the length and breadth of a Mr. Aqua OHF filter box.

I have been using filter wool, which compresses over time in the IOS. It becomes less effective then. I have tried many brands of filter wool and the same thing happens.

I have thought of using bio-sponge but can't seem to find a piece with the correct dimensions.

Are there alternative mechanical filtration media of a suitable size?

Thank you!