• Concentrated powder format — mix your own stock solution rather than paying to ship and store a pre-mixed liquid.
• 1 mL raises calcium by 2 ppm per 100 L — a precise, repeatable dosing rate once mixed to solution.
• Under 1c per litre of tank water treated — both pack sizes work out to a fraction of a cent per litre at standard maintenance dosing.
• Part of the Foundation ABC+ system — designed to be dosed alongside Foundation B (Alkalinity) and Foundation C (Magnesium), in that order.
• Strontium included — supports skeletal density alongside calcium.

Dissolve the full 1 kg tub in 1.8 L of RO/DI water to make a concentrated stock solution. Once mixed, 1 mL of that stock solution raises the calcium level of 100 L of tank water by approximately 2 ppm. Dose to a tested target, not a fixed schedule — test calcium before dosing and adjust the volume to what your system is actually consuming.

What calcium range should I be running?

Red Sea's own guidance puts the target between 410 mg/L for a low-nutrient system and 465 mg/L for an SPS-dominated frag tank. Match the target to your system type rather than chasing the highest number on the chart.

How much can I safely raise calcium in one day?

Red Sea's stated maximum is 20 ppm in 24 hours. Raising it faster risks stressing corals even though the number itself isn't dangerous to fish.

Can I dose Foundation A, B and C together?

Yes — Red Sea's recommended order is magnesium first, then alkalinity, then calcium, with roughly 10 minutes between each so the three don't react with each other before they've dispersed through the water column.

Suitable for reef and marine aquariums keeping stony coral, soft coral or coralline algae that need ongoing calcium replacement. Not suitable for freshwater aquariums, and not a substitute for testing — dosing calcium without testing risks pushing the system toward saturation, which can crash alkalinity.

Handle the dry powder the same way as any concentrated mineral supplement: avoid inhaling dust when measuring, and keep it away from children and pets. Once mixed to solution, dose into a high-flow area of the sump rather than directly onto livestock.

Store the tub sealed, dry and out of direct sunlight. Once mixed, keep the stock solution in a sealed, opaque container — light and air both shorten its working life. Re-test calcium weekly and adjust the daily dose rather than assuming consumption stays constant as coral cover grows.

Consumable supplement — check the use-by guidance on the tub rather than a fixed warranty term, and your rights under Australian Consumer Law apply regardless. Standard freight; the 18 kg pail ships as a heavier parcel.

• Red Sea Foundation B (Alkalinity+) — dosed alongside Foundation A in the three-part program.
• Red Sea Foundation C (Magnesium+) — the third element in the ABC+ program.
• Red Sea Reef Care Dosing Cap Tube — for connecting a stock solution bottle to a dosing pump.

Is Foundation A the same as Reef Foundation ABC+?

No — ABC+ is Red Sea's name for the combined three-part program. Foundation A is the calcium and strontium element on its own, for reefkeepers who want to dose and test each parameter independently.

Do I need the 18 kg pail or the 1 kg tub?

Per-litre cost favours the 18 kg pail, but only if you'll use it within its working life once mixed — for a smaller system, the 1 kg tub avoids stock solution sitting around for months.

Will this raise magnesium or alkalinity too?

No — Foundation A is calcium and strontium only. Alkalinity and magnesium are dosed separately with Foundation B and C.

Can I use this instead of a calcium reactor?

Yes, on smaller to mid-sized reef systems many keepers dose Foundation A instead of running a reactor. On larger, heavily stocked SPS systems a reactor is usually more cost-effective long-term.