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Filtration

A well-filtered pond needs to handle much higher biological loads than an indoor aquarium. Koi produce 10 to 15 times more waste per kilogram of body weight than tropical fish.

Types of Pond Filters

Biological Chamber Filter (Pond Filter)

The most common type for medium-sized ponds. Water flows through chambers containing filter media:

  1. Sedimentation chamber: Traps large particles
  2. Biological chamber: Porous media (bio-balls, K1, lava) containing nitrifying bacteria
  3. Polishing Chamber: Fine sponges for water clarity

Vortex settler

For serious koi ponds. The water circulates, and solids settle at the bottom of the conical chamber to be removed. Very efficient for pre-filtration before the biofilter.

Drum filter (Automatic drum)

High-end. A 60–100 µm rotating mesh that automatically removes solids through water backwashing. The most efficient option for koi. Self-cleaning.

A natural shelter made of plants

Ponds with dense vegetation and a large area of exposed rock may not require a conventional mechanical filter (the "natural swimming pond" method). This is only feasible with a low fish load.

Filtration Capacity

For koi, filter the entire volume of the pond at least 1–2 times per hour. A 5,000-liter pond requires a pump with a flow rate of 5,000–10,000 liters per hour.

UV in a pond

A UV sterilizer in the filtration system:

  • Removes green algae (suspended phytoplankton)
  • Reduces pathogens in water
  • It DOES NOT kill parasites in fish (only free-living ones)
  • Sizing: 1 W of UV per 1,000–2,000 L of water