• Buffer and trace elements in one bottle — carbonate buffers, potassium and trace elements including iron, in the proportions Red Sea states coralline algae consume.
• A published dose response — 1 mL raises alkalinity in 100 L by 0.1 dKH (0.03 meq/L), so you dose against a test result instead of guessing.
• Replaces Reef Foundation B in these systems — Red Sea specifies KH Coralline Gro instead of the Foundation B buffer while cycling a new marine tank, and on an ongoing basis in fish-only or soft coral systems.
• Coralline competes with nuisance algae — Red Sea's stated rationale is that encrusting coralline takes up the nutrients and rock surface pest algae would otherwise use.
• Three pack sizes, one formulation — 100 mL, 500 mL and 5 L all dose at the same rate.

The formulation and the dose rate are identical across all three. Size is only a question of how quickly you get through it.

Red Sea does not publish a fixed millilitres-per-litre dose. The dose is derived from your own alkalinity test, because you are replacing what the tank has consumed.

Setting the daily dose

Red Sea's procedure for boosting coralline algae, from the product manual:

1. Run the aquarium for four days at stable salinity, compensating for evaporation daily, without adding any supplements.
2. Test alkalinity and calculate the dose needed to bring it back to target. That is the four-day dosage.
3. Add the four-day dosage to the system. Divide it by four and use that as the daily dose for the next week.
4. After a week of daily dosing, test again and adjust.
5. Keep testing weekly and adjusting the daily dose as required.

The rules that matter

• Check salinity and correct it before testing alkalinity, then wait 10 minutes for the water to stabilise.
• Never move alkalinity by more than 0.5 meq/L (1.4 dKH) in one day. Faster than that stresses corals.
• Add it to the sump. With no sump, add it slowly into an area of high flow so it never contacts corals directly.
• If you miss a day or more, add the full missed amount — but not where that would breach the daily ceiling above.

Suitable for

• Cycling a new marine aquarium, where Red Sea specifies it in place of Foundation B
• Fish-only marine systems
• Soft coral systems
• Encouraging coralline onto bare rock, returns and overflow boxes

Not suitable for

• Use alongside Red Sea Foundation ABC+. Red Sea states the two should not be used in conjunction.
• Reef systems already dosed for hard corals. Red Sea is blunt about this: coralline algae will grow naturally, without any special supplements, in all reef systems optimised for hard corals. If calcium, alkalinity and magnesium are already held at stony coral levels and you supplement trace elements, this product has nothing to add.
• Freshwater aquariums. This is a marine formulation.

• Red Sea KH/Alkalinity Pro Test Kit — the kit Red Sea names for measuring the drop this product replaces. Its 0.05 meq/L resolution is what makes the four-day method work.
• Red Sea Marine Care Multi Test Kit — pH, ammonia, nitrite and nitrate, for the cycling period when you would be dosing this.
• Red Sea Marine Care Magnesium Test Kit — low magnesium is the usual reason alkalinity will not hold its level.
• Red Sea Marine Care Calcium Test Kit — calcium and alkalinity move together and are best read as a pair.
• Red Sea Coral Pro Salt — start water changes from a known alkalinity baseline.

Red Sea's 24-month warranty covers manufacturing defects in its aquarium products and expressly excludes consumable items. Red Sea publishes no separate warranty term for its supplements. Any manufacturer warranty is in addition to your rights under the Australian Consumer Law and does not limit them.

Red Sea does not publish storage conditions, a shelf life or a safety data sheet for KH Coralline Gro, so this page does not state one. If you need a dangerous goods or air freight classification for the 5 L, contact us before ordering and we will confirm it with the distributor.

How much Red Sea KH Coralline Gro do I add per litre?

There is no fixed per-litre dose. Red Sea sets the dose from a measured alkalinity drop: 1 mL of KH Coralline Gro raises the alkalinity of 100 litres of aquarium water by 0.1 dKH, so you test, calculate the shortfall against your target, and dose to close it — never moving alkalinity more than 0.5 meq/L (1.4 dKH) in a single day.

Can I use KH Coralline Gro and Red Sea Foundation ABC+ together?

No. Red Sea states in the KH Coralline Gro manual that it should not be used in conjunction with Red Sea Foundation ABC+. KH Coralline Gro is used instead of the Reef Foundation B buffer, not alongside the full Foundation program.

Do I need KH Coralline Gro if I run a hard coral reef?

Usually not. Red Sea states that coralline algae will grow naturally, without any special supplements, in all reef systems optimised for hard corals — meaning systems where calcium, carbonates and magnesium are held at stony coral levels and trace elements are already supplemented. KH Coralline Gro is aimed at fish-only systems, soft coral systems and new tanks being cycled.

What alkalinity should I be aiming for?

Red Sea specifies approximately 3 meq/L, which is 8.4 dKH, to promote coralline algae in fish-only and soft coral aquariums. That is deliberately lower than the 11 to 12 dKH many stony coral keepers run.

Which test kit should I use with it?

Red Sea names its Reef Foundation KH/Alkalinity Pro Test Kit, which resolves to 0.05 meq/L (0.14 dKH) across 75 tests. That resolution matters, because the dosing method depends on detecting a small alkalinity drop over four days.

Where in the tank do I add it?

Into the sump. If the system has no sump, Red Sea says to add the supplement slowly into an area of high water flow to prevent direct contact with the corals.