Biohome media should only be placed behind an effective mechanical filter. This is usually open pore reticulated filter foam.
While open pore foam is readily available and quite inexpensive, you should be aware that most of this foam it is not suitable for use in an aquarium filter. All foam used in packaging and construction must contain flame inhibitors. This is impregnated in the foam and will leach out over time and is not something you want in your aquarium water.
GreatWave Filter Foam is a genuine filter foam. We have tested it for some time in an aquarium and on our koi quarantine tank to insure it has no harmful effects on the fish.
A Medium Foam sheet is 13″ x 13″ x 1″ thick 20 ppi convoluted foam. The foam can easily be cut to the appropriate size and shape for your filter with a sharp knife.
Note: Nominal sheet size is 13″x13″. Actual size may vary a bit.
It should be placed in your filter where the water enters after a sheet of Coarse foam.