Filter Media
High-capacity phosphate control for serious reefs
Nereus GFO (granular ferric oxide) is selected for reef aquariums that need reliable phosphate and silicate binding without clouding the system. It is the kind of media used in international reefing workflows - reactor-ready, low-dust, and sized for consistent contact time.
When phosphate climbs, nuisance algae follows and coral colour can dull. GFO pulls dissolved PO? out of the water column so your skimmer, lights and husbandry can do their jobs again.
Why reefers choose it
- Strong adsorption of phosphate and silicate
- Low-dust granules for cleaner reactor starts
- Suitable for media reactors or high-flow media bags
- Pairs cleanly with PhoX when you need a faster knockdown
- Consistent particle size for even flow and longer useful life
How to use
- Rinse thoroughly in RODI water until the runoff runs clear. This removes fines that can cloud the display.
- Dose by volume, not guesswork - start conservatively (often about 1 tablespoon per 40-50 L / 10-13 US gal as a starting point for many systems) and adjust from test results.
- Run in a reactor with a gentle tumble, or in a filter sock / media bag where water must pass through the bed. Avoid blasting the media into a powder.
- Test phosphate every few days after a media change. When effluent PO? stops dropping or climbs again, replace the charge.
- Change gradually on sensitive SPS systems - sudden phosphate crashes can stress corals. Split large replacements across a few days if needed.
Best practice
- Pre-filter water going into the reactor to keep organics off the media surface.
- Do not mix GFO in the same chamber as carbon unless your reactor is designed for it - they prefer dedicated stages.
- Store sealed and dry between uses.
GFO is a refinement tool, not a substitute for feeding control and export. Use it as part of a stable nutrient strategy alongside the Nereus dashboard trends you already watch.