Proper filtration is the life support system for your koi pond. A well-designed filtration system handles mechanical removal, biological conversion, and sterilization.
Types of filtration:
Mechanical: Removes solid particles (fish waste, debris). Examples: bead filters, drum filters, settlement chambers, brushes, matting.Biological: Houses beneficial bacteria that process ammonia and nitrite. Examples: moving bed (K1 media), static media, shower filters, bog filters.UV Sterilization: Kills free-floating algae and some pathogens. Replace bulbs annually even if still lit -- UV output declines over time.Chemical (optional): Activated carbon removes dissolved organics, medications, and odors. Zeolite can temporarily absorb ammonia in emergencies.Sizing rules of thumb:
Total filter turnover: 1-2x pond volume per hour minimumPump sizing: match to your filter's maximum flow rateBiological media: more is better, but ensure adequate flow through itMaintenance guidelines:
Mechanical media: clean weekly to biweeklyBiological media: rinse in pond water only, NEVER tap water (chlorine kills bacteria)Never clean all filter media at once -- stagger to preserve bacterial coloniesUV bulbs: replace annually at spring startupPumps: inspect monthly for debris, check impeller annually