I finally got over the fire retardant warnings when last January I bought one huge bag of "Buffalo Snow" for $1 a bag at Walmarts after Christmas close-out sale. Thinner then Poly Batten only 1/4 inch thick in a big blanket role intended to lay under the Christmas tree and look like a blanket of snow.
Anyway after testing it (fire retardant treated) in my feeder tank filters wil no ill affects, I have been using the stuff in all my tank filters becasue its thinner and easier to work with then poly blanket and way-way cheaper for the same amount. Even when not on sale during Christmas its only $3 a bag. Ill be at the next clearance sale at Walmart after News Years to stock up on several $1 bags next time.