Filtreau Excellent Combi Drum 25/30 – Gravity Fed

Filtreau Excellent Combi Drum 25/30 – Gravity Fed

Automatic mechanical and biological filtration for a purpose-built koi pond

The Filtreau Excellent Combi 25/30 is a practical starting point for a purpose-built koi pond with bottom drains, a skimmer and a dedicated filter area. It removes solid waste automatically, then provides space for biological treatment before the water returns to the pond. An 80W high-output UV-C unit helps tackle suspended green-water algae.

This is the standard-height gravity-fed model, rather than the shorter Low version. Its 985 mm body height and 1,200 × 1,117 mm footprint are worth comparing with the available space before choosing: a filter that fits neatly on paper still needs room for valves, pipe bends and servicing above the lid.

Solids out first, biological treatment second

Water entering through the bottom-drain and skimmer lines passes through a 120-micron screen. As dirt builds up and changes the water level, the control system starts a rinse. The drum turns while the internal wash pump supplies the spray bar, carrying collected waste into the waste outlet instead of leaving it to break down in the biological section.

The biological chambers do a different job. Moving-bed media provides surfaces for bacteria that convert ammonia and nitrite, while a separate matting section provides a fixed-media stage. Those bacteria need time, oxygen and a sensible feeding load to establish. A new filter is not immediately ready for the maximum fish load simply because its drum is already cleaning itself.

Choosing the media and air supply

Hel-X and Japanese matting are separate media choices for this model. The optional media arrangement includes 100 litres of Hel-X and 2 m² of matting; that is a package configuration, not a reason to pack every space solid. Keep the moving-bed media free to circulate and the matting accessible for cleaning.

Our high-quality Japanese matting comes in sheets measuring 1.2 × 1 m. Two uncut sheets provide 2.4 m² before trimming; their cutting layout and thickness still need to suit the chamber. They are not sold as a factory cartridge. An external air pump is also needed to supply the two fitted air bars. Size it for the media load and operating depth, not its headline output in open air.

Matching the filter to the pond

Maximum water flow is 30,000 litres/hour, with a maximum koi-pond rating of 25,000 litres. These are different measurements. A pond stocked heavily and fed generously may need more biological capacity than another pond of the same volume. Allow useful operating headroom rather than designing every pipe and pump around the absolute limit.

For a shallower installation, compare the 25/30 Low gravity-fed model. If your pump sends dirty water up from the pond, choose the pump-fed 25/30 instead; changing the plumbing alone does not make the gravity configuration interchangeable.

Technical details

Planning access and routine care

Set the filter on a level, fully supported base at the correct operating water level. Plan isolation valves on the inlet branches, access to the waste connection and enough space to remove the lamp and quartz without dismantling the surrounding pipework. The circulation pump is separate from the drum-cleaning pump.

Check the waste channel, spray pattern and screen regularly, even though rinsing is automatic. A blocked waste pipe or restricted drain line will not be cured by increasing the pump speed. Use the Excellent filter manual for safe maintenance, and keep the screen away from a pressure-washer jet.

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• View Filtreau UV-C units
• Find replacement UV lamps and quartz sleeves