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Water Chemistry

GFO vs Lanthanum Chloride: Choosing a Phosphate Removal Method

How GFO media and LaCl3 dosing compare for stripping phosphate, plus the best workflow for each.

By Saltwater Aquarium Guide Published May 10, 2026

Assorted colourful corals photographed against a dark background — Photo: David Clode / Unsplash

Both methods remove phosphate effectively. They suit different tank sizes and different operator personalities.

GFO (granular ferric oxide)

Passive, predictable, slow. Set in a fluidized reactor and forget for 4–8 weeks. Safe for any reef.

Lanthanum chloride

Active, fast, requires careful dosing. Drip into a 5-micron filter sock to capture LaPO4 precipitate. Crashes phosphate fast — do not overdose.