Foundation A Calcium+ 500ml — Calcium, Strontium and Barium for Corals - Red Sea

Foundation A Calcium+ from Red Sea supplies the three elements stony corals draw on to build their skeleton: calcium, strontium and barium, in the ratios found in coral skeleton itself. 500ml liquid bottle.

Red Sea explains the Foundation program in its own words:

And for a longer walk-through of the whole Reef Care Program — major elements, trace elements, algae management and coral nutrition — this independent explainer covers the ground well:

Why strontium and barium matter

A coral builds roughly 90% of its skeleton by combining calcium and carbonate from the water into aragonite. The remainder comes from magnesite, strontianite, calcite, fluorite and other minor minerals.

Here is where it gets interesting: when magnesium or strontium run low, the skeleton forms with a higher proportion of calcite — a more brittle crystal structure, more prone to damage. Adding calcium alone does not fix that. It is the whole reason this is a calcium-strontium-barium blend rather than a plain calcium solution.

Specifications

• Elements: calcium, strontium and barium
• Concentration: 1ml raises calcium in 100 litres (25 gal) by 2ppm
• Daily maximum: 20ppm of calcium per day
• Sizes: 250ml, 500ml (this listing), 1L, 5L and 1kg powder
• Suitable for: reef aquariums with SPS, LPS and soft corals · dosing pump compatible

Target levels for your reef tank

Red Sea publishes different targets depending on the coral population. An SPS frag tank is not run like a mixed reef.

Pick the row matching the most demanding species in your saltwater tank.

How to dose: the manufacturer's method

The "1ml = 2ppm" figure is not a dose — it converts a measured gap into millilitres. Red Sea describes a specific method for finding your daily dose:

1. Bring all three elements (Ca, Alk, Mg) to their target values.
2. Run the tank for 4 days without dosing anything, topping up evaporation with fresh water.
3. Test. Work out the dose needed to return to target: that is your "4 day dosage". Add it.
4. Divide it by 4: that is your daily dose for the coming week.
5. Retest weekly and adjust. Uptake changes as corals grow.

Three rules not to skip

• Daily maximums: calcium 20ppm, alkalinity 0.5 meq/l (1.4 dKH), magnesium 10ppm. Larger gaps get spread over several days, never dumped in at once.
• Dosing order: magnesium first, alkalinity second, calcium last — 10 minutes between each. The reverse order causes precipitation.
• Where to add it: into the sump. Without a sump, slowly into a high-flow area to avoid direct contact with fish and corals.

One last trap: adding calcium to saturation levels causes a sudden drop in alkalinity. The three elements hold each other up; they are not managed separately.

Goes well with

Calcium does not work alone. Foundation B KH/Alkalinity supplies the carbonates without which calcium cannot form aragonite, and Foundation C Magnesium keeps calcium and alkalinity from precipitating against each other. Low magnesium is the single most common reason alkalinity refuses to hold.

To start with all three, the Foundation ABC 3x250ml trio costs less than three separate bottles. Once the base is stable, Trace Colors ABCD takes over with the 31 trace elements tied to coral colour.

Frequently asked questions

How much calcium can I add in one day?

Red Sea caps it at 20ppm per day to avoid stressing corals. If your gap is larger, spread it across several days while respecting that daily ceiling.

In what order should Foundation A, B and C be dosed?

Magnesium (C) first, alkalinity (B) second, calcium (A) last, with 10 minutes between each addition. That is the manufacturer's sequence, and it prevents precipitation.

My calcium will not rise despite dosing — why?

Red Sea lists three classic causes: new aragonite substrate precipitating calcium and carbonates, an unbalanced salt mix (low magnesium or high calcium), or excess buffer added while calcium was already at saturation. Test magnesium before dosing more calcium.

Can it be used with a dosing pump?

Yes. Add it to the sump, or failing that slowly into a high-flow area.

Why buy from ReefSolution

Aquarium ReefSolution is an authorized Red Sea dealer. Our team works in marine aquariums in Laval and knows the Reef Care Program from real tanks. We ship across Canada and offer in-store pickup.