Foundation B KH/Alkalinity 500ml — Stable Alkalinity and pH in Reef Tanks - Red Sea

Foundation B KH/Alkalinity from Red Sea is a complex of carbonate and other buffers present in seawater that hold alkalinity and pH where they belong. 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:

What alkalinity actually measures

Alkalinity is not "the carbonate level". It measures every buffering substance in the water: bicarbonate (HCO₃), carbonate (CO₃), hydroxide (OH) and borate (BO₃). That distinction has a practical consequence — Red Sea advises avoiding test kits that measure carbonates only, because they do not report total alkalinity and will throw off every dosing calculation you make.

Two units coexist in the hobby: milliequivalents per litre (meq/l) and degrees of carbonate hardness (dKH). The conversion is simple: dKH = meq/l × 2.8.

Specifications

• Composition: carbonate and other seawater buffers
• Concentration: 1ml raises alkalinity in 100 litres (25 gal) by 0.036 meq/l (0.1 dKH)
• Daily maximum: 0.5 meq/l, or 1.4 dKH 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

⚠️ The powder version is not the same strength as the liquid: 1g raises alkalinity in 100 litres by 0.12 meq/l (0.33 dKH), and 1kg makes 10L of stock solution. Never carry a calculation from one format to the other.

Target levels for your reef tank

A detail that surprises a lot of reef keepers: an SPS dominant tank targets LOWER alkalinity (8.0 dKH) than a mixed reef (11.5). When you drop nutrients to bring out colour, balanced but lower foundation levels put less stress on the corals.

How to dose: the manufacturer's method

The "1ml = 0.1 dKH" figure converts a measured gap into millilitres — it is not a daily dose. Red Sea's method for finding your dose:

1. Bring Ca, Alk and Mg to their targets.
2. Run 4 days without dosing anything, topping up evaporation with fresh water.
3. Test, work out the dose to return to target, add it.
4. Divide by 4: that is your daily dose for the week.
5. Retest weekly and adjust.

Three rules not to skip

• Daily maximums: alkalinity 0.5 meq/l (1.4 dKH), calcium 20ppm, magnesium 10ppm. Big gaps get spread over several days.
• Dosing order: magnesium, then alkalinity, then calcium — 10 minutes between each.
• Where to add it: into the sump, or slowly into a high-flow area.

Watch the reverse trap too: adding buffer to a tank whose calcium is already at saturation causes precipitation and drops the calcium. Always test first.

Goes well with

Alkalinity that refuses to hold very often traces back to low magnesium — Red Sea lists it as a classic cause. Before raising the buffer, check with Foundation C Magnesium. And alkalinity builds nothing without calcium: Foundation A Calcium+ supplies the calcium, strontium and barium of coral skeleton.

For all three at once, the Foundation ABC 3x250ml trio. Once the base is stable, Trace Colors ABCD covers the 31 trace elements tied to coral pigments.

Frequently asked questions

My alkalinity keeps dropping — why?

Red Sea identifies three common causes: new aragonite substrate precipitating calcium and carbonates, an unbalanced salt mix with low magnesium or high calcium, and excessive calcium dosing without magnesium. Test magnesium first.

How much can I raise alkalinity in one day?

By 0.5 meq/l at most, which is 1.4 dKH. Beyond that, spread it over several days while respecting the daily ceiling.

What alkalinity should I target in an SPS tank?

Red Sea recommends 8.0 dKH for an SPS dominant tank and 12.6 dKH for an SPS frag tank — the targets differ depending on whether you are chasing colour or fast growth.

What is the difference between meq/l and dKH?

They are two units of the same measurement: dKH = meq/l × 2.8. Red Sea publishes its values in both.

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.