The Use Of A Biological Filter Will Remove These Toxins (Ammonia, Nitrite) And Provide Good Quality Water With The Additional Benefit Of Reducing Algae Growth. There Are Two Stages Of Filtration In Every Bio-Master Filter Stage 1 Mechanical – Suspended Particles Are Filtered As The Water Passes Through Layers Of Foam. Green Foam: Course Grade White Foam: Medium Grade (Excluding 3000 Model) Blue Foam: Fine Grade Stage 2 Biological – Below The Layers Of Foam, There Is Biological Media Called FlocorTM. The Purpose Of This Media Is To Allow Beneficial Bacteria To Grow On It’S Surface. Once Matured The Bacteria Will Breakdown The Harmful Pond Pollutants (Ammonia & Nitrite) Converting Them Into Nitrate… Which Is Naturally Absorbed By Pond Plants.