Reef Carbonate

  • Raises carbonate alkalinity (KH)
  • Concentrated (4,000 meq/L)
  • Made with a blend of carbonate and bicarbonate salts


Reef Carbonate™ is a concentrated (4,000 meq/L) optimized blend of carbonate and bicarbonate salts designed to restore and maintain alkalinity in the reef aquarium. Calcium and carbonates are essential to all coral growth. If either becomes deficient, coral growth will cease, followed by a rapid decline in coral health. To prevent this you must provide carbonates (Reef Carbonate™) and calcium (Reef Advantage Calcium™ or Reef Complete®).

Whereas competing products simply use sodium bicarbonate, Reef Carbonate™ is made with a blend of carbonate and bicarbonate salts. This blend of salts results in 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 Reef Carbonate’s™ 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.

Used as directed, Reef Carbonate™ will not deplete calcium, magnesium, or strontium which usually tend to precipitate with increasing alkalinity. Reef alkalinity should be maintained at 3–5 meq/L (8–14 dKH). Alkalinity should not be allowed to fall below 2 meq/L.


BEGINNER: Use 1 capful (5 mL) per 80 L (20 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, then follow addition regimen above until alkalinity is adjusted to 4–5 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 to determine how much to add to your top–off 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 top–off 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 & Alkalinity to measure total alkalinity or Reef Status™ Magnesium, Carbonate & 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 & carbonate additives are added on alternate days or at least 30 minutes apart.


100 mL, 250 mL, 500 mL, 2 L

To reach your desired level use:

caps or mL

Do not exceed 1 meq/L (.25 US gallons) per day

Considerations: Reef alkalinity should ideally be maintained at 4-5 meq/L (11-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts. Each dose will raise alkalinity by about 0.25 meq/L.

A: The white crystals you see are normal for that product when exposed to cold temperature. Once the product warms up, you should be able to shake the bottle and get them to re-dissolve. If you have a hard time getting the crystals to re-dissolve, try heating some water (luke warm) on the stove and setting the bottle in the water for a few minutes before shaking.

A: Reef Builder is the powdered version of Reef Carbonate. They are identical products for the most part. There is a slightly different blend of salts used to make Reef Carbonate than the salts used in Reef Builder. We do this to make Reef Carbonate (liquid) as concentrated as possible. The end result is the same regardless of the product you choose.

A: No, Reef Carbonate will not be impacted by a canister or protein skimmer. It is perfectly acceptable to leave this equipment running while dosing this supplement.

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0665 Reef Carbonate 100 mL
0666 Reef Carbonate 250 mL
0663 Reef Carbonate 500 mL
0668 Reef Carbonate 2 L