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.
We are happy to announce that GreatWave is now selling the very best filter foam available, Poret Foam. We have tested it for some time and now proud to supply the best foam at a great price.
The Foam Filter set consists of one sheet of 13″ x 13″ x 1″ thick 10 ppi flat foam, one sheet of 13″ x 13″ x 1″ thick 20 ppi flat foam and one sheet of 13″ x 13″ x 1/2″ 45 ppi flat foam. The foam can easily be cut to the appropriate size and shape for your filter with a sharp knife.
It should be placed in your filter where the water enters in this order: Coarse, Medium and Fine.