Found a source for pre filter material.....

[Amadhunter]

I hope, unless someone knows of a reason not to use this stuff, here it is:
While looking for some spongey material at wal mart, I found this insulating material for sealing the space between windows while using a window unit type air conditioner. It's square, and has small pores, easy to cut to size, shape, and fit for HOB filters. I'm now using it on my tanks, and so far no problems. It's cheap too, it cost me about $2.00 for 42" long x 2 1/4 x 2 1/4.
The name on the pkg is Window Air Conditioner Insulating Seal. Here's a pic of it on my 75 gal, HOB filter:

[Amadhunter]

Another shot:

[Amadhunter]

This is the stuff in the pkg:

[ronrca]

It may be fine to use I hope. If it mentioned anything about antibacterial, antimold, etc though, I would not use it as these types of chemicals that fight bacteria and mold may leach into the water and who knows what effect it may have.

I actually use sponge from sewing/fabric stores. It comes in 24" x whatever length you want. Its pretty cheap and all you have to do is cut to whatever size. But make sure its not dyed but white.

[Carol_Roberts]

I like the fine pores on your sponge madhunter. Like Ron says - make sure there is nothing about anti mold/ anti bacterial

[Amadhunter]

It dosen't say on the pkg that it's anti mould, bacteria or has any chemical insecticides in it. It's been on my community tank for 4 days now with no ill effects. I'll keep an eye on it.