Collection: Magnesium

Chloride and sulphate together

Magnesium is dosed in a reef because it holds calcium and alkalinity in solution at levels seawater would otherwise not sustain. Reef aquarists generally combine magnesium chloride and magnesium sulphate rather than using either alone, so the finished supplement carries a chloride-to-sulphate balance closer to natural seawater. That is why both salts are stocked here in two sizes each.

Mixing from bulk

• Both salts are made up with RO water before dosing, not added dry to the tank.
• Working from bulk puts the ratio and the strength of the mix under your control.
• Bag quantities and water volumes are printed on the packaging.
• Mixed solution is stored sealed and labelled, away from the calcium and alkalinity parts.

Bulk salts or a ready-made mix

Buying magnesium as raw salt suits anyone dosing a larger system or working to their own recipe, where the volume involved makes premixed bottles impractical. If you would rather not mix at all, the ready-made magnesium component sits with the three-part system in Calcium & Alkalinity instead. Test before adjusting magnesium rather than dosing to a schedule, since it moves far more slowly than calcium or alkalinity in most tanks.