I found a few sources online, but they don't list if there are any antimicrobial chemicals or if they are aquarium safe. I am looking to fill 3 FX5 filters with foam for extra mechanical filtration and also put them in between the baffles on my sumps. Ideally looking for 2-2.5" thick sheets of sponge or "foam". Thought I would give this a try before getting the Fluval Biofoam inserts for Fx5/Fx6 at $10/box of 2.