Filtration

Filtration is the life-support system of a koi pond. Koi produce far more waste per body mass than most freshwater fish, and a pond without adequate mechanical and biological filtration will develop toxic ammonia and nitrite levels within days. The filtration system must process the entire pond volume at least once every two hours — ideally once per hour.

Effective koi pond filtration operates in three stages: mechanical removal of solid waste, biological conversion of dissolved ammonia to less toxic nitrate, and optional chemical polishing for clarity and phosphate control. Understanding how each stage works — and how they interact — is the foundation for choosing, sizing, and maintaining your system.

Guides in This Section

Filtration Principles

The science behind mechanical, biological, and chemical filtration — how each stage works and why the sequence matters.

Filter Types

Bead filters, drum filters, moving bed (MBBR), shower filters, bog filters, and multi-bay systems compared.

Pump Selection & Sizing

Flow rate calculations, head pressure charts, energy efficiency, and matching pump output to your filter system.

UV Clarifiers

How UV sterilizers control green water, proper sizing by pond volume, bulb replacement schedules, and flow rate limits.

Filter Maintenance

Cleaning schedules, when to rinse vs replace media, protecting beneficial bacteria during maintenance, and seasonal adjustments.

DIY Filter Builds

Build plans for gravity-fed settlement chambers, multi-bay biological filters, and shower filter systems using affordable materials.

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