Sera siporax pond Protectsera siporax pond protect Professional Abrasion proof high performance filter medium for all pond filter setups sera siporax pond protect Professional is the biological filter medium with a protecting ball preventing abrasion, which was specially developed for use in filter setups with strong water agitation. The outer cover protects the internal siporax ring and directs the water current directly into it. Water flow through the sintered glass ring is