Seachem Reef Carbonate 250ml (SC-666)

New product

  • Provides carbonate for coral growth
  • Raises carbonate alkalinity (KH)
  • Concentrated (4,000 meq/L)
  • Contains a blend of carbonate and bicarbonate salts

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$ 9.30

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Brand: Seachem

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Seachem Reef Carbonate 250ml (SC-666)

Calcium and carbonates are essential for coral growth. A deficiency of either component causes coral to stop developing. Use Seachem Reef Carbonate to replenish carbonates to ensure a thriving coral community. Seachem Reef Carbonate is a concentrated (4,000 meq/L), optimised blend of carbonate and bicarbonate salts designed to restore and maintain alkalinity in the reef aquarium.

Used as directed, Seachem Reef Carbonate will not deplete calcium, magnesium, or strontium which usually tend to precipitate with increasing alkalinity. Reef alkalinity should be maintained at 36 meq/L (817 dKH). Alkalinity should not be allowed to fall below 2 meq/L.

For calcium dosing, you have the choice of either Seachem Reef Advantage Calcium or Seachem Reef Complete.

Seachem Reef Carbonate vs Others

Whereas competing products simply use sodium bicarbonate, Seachem Reef Carbonate is made with a blend of carbonate and bicarbonate salts. This blend of salts results in Seachem Reef Carbonate yielding a pK of roughly 9.0 in saltwater (higher than competing products).

In a closed reef system, the multitude of organics produced by reef inhabitants tends to force pH downward, but the advantage of Seachem Reef Carbonates higher pK is a stabilization of pH around 8.3-8.4. Competing products formulations make them incapable of such a claim, so pH will always fall below desirable levels for a reef aquarium.


  • Beginner: Use 1 capful (5 ml) per 80 L (20 US gallons) twice a week. Best if diluted into a cup of freshwater, then added. Check alkalinity every 2 weeks and adjust amount or frequency accordingly.
  • Advanced: Check alkalinity (use MultiTest Marine pH and Alkalinity to test alkalinity levels), then follow addition regimen above until alkalinity is adjusted to 45 meq/L. Each ml contains a minimum of 4 meq of alkalinity. Each 5 ml/80 L will raise alkalinity by about 0.25 meq/L. Amount or frequency can be adjusted, but do not exceed 20 ml/80 L per day. Thereafter, use as required to maintain alkalinity.
  • Expert: After determining the alkalinity consumption rate, set up a continuous drip system. Use the following formula (or skip the math and use our Dosage Calculator) to determine how much to add to your topoff water: m=va/4 (m=ml of product to add to top off water, v=volume of tank in liters, a=amount to raise alkalinity in meq/L). For example, if you want to raise alkalinity by 1 meq/L in a 200 liter tank, then you would add (200x1)/4=50 ml into the topoff water. [For reference: 1 gallon=3.8 L].
  • Notes: Best to pour in gradually near strong water movement. Do not add to a sump or other area of slow water exchange. Use MultiTest: Marine pH and Alkalinity to measure total alkalinity or Reef Status Magnesium, Carbonate and Borate to measure carbonate alkalinity.DO NOT OVERDOSE: Excess alkalinity may enhance the loss of calcium, magnesium, and strontium. Do not directly mix with any calcium, magnesium, or strontium supplement. Best if calcium and carbonate additives are added on alternate days or at least 30 minutes apart.

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