Seachem Reef Calcium

Reef Calcium is a concentrated (50,000 mg/L) bioavailable polygluconate complexed calcium intended to maintain calcium in the reef aquarium without altering pH. Polygluconate complexation confers several benefits: it increases the bioavailability of the calcium, it provides a rich source of metabolic energy to help maintain peak coral growth, and it prevents calcium precipitation/alkalinity depletion. Polygluconate contains no nitrogen or phosphorous, thus it is biologically impossible for it to lead to algae growth in a properly maintained reef system. Reef Calcium may be used alone to maintain calcium but will provide enhanced levels of coral growth when used in conjunction with an ionic calcium supplement (Reef Complete,Reef Advantage Calcium). Reef Calcium is intended to maintain calcium levels; if calcium becomes seriously depleted one should either perform a water change or use an ionic calcium supplement to restore the depleted level of calcium.

Sizes: 250 mL

Reef Calcium utilizes a chained organic calcium rather than an ionic calcium. When a coral absorbs a molecule into its tissue, it uses the same amount of energy regardless of molecular size. However, charged molecules require more energy. When an uncharged molecule of Reef Calcium is absorbed, the coral acquires multiple calcium atoms as well as an easily metabolized carbohydrate with less energy expended than it uses for ionic calcium uptake. Therefore, at lower calcium levels, corals can still take in as much calcium through our organic chains as they would at much higher levels of ionic calcium.

Add 1 capful (5 mL) per 80 L (20 gallons*) twice a week. You can increase the amount or frequency based on growth response but do not exceed 3 capfuls per 80 L (20 gallons*) per day. Each capful will raise calcium by about 3 mg/L. HINTS: Use the Reef Status Calciumtest kit to measure calcium. It is not necessary to exceed 380 mg/L total calcium when using this product. Color and clarity may vary between lots.

Amounts per 1 g

Compatibility

Reef aquariums. Seachem item #0356. It maintains calcium without altering pH, and because polygluconate contains no nitrogen and no phosphorus, Seachem’s position is that it is biologically impossible for it to drive algae growth in a properly maintained reef.

It maintains; it does not restore. This is the distinction that decides whether it is the right product for you. If calcium is seriously depleted, Seachem’s own instruction is to do a water change or use an ionic calcium supplement to bring it back, and then use this to hold it. Each capful raises calcium by only about 3 mg/L.

It works best alongside an ionic calcium supplement — Reef Complete or Reef Advantage Calcium. Used alone it will maintain the level; used with one of those, Seachem claim enhanced coral growth. The two are complementary rather than alternatives, because this one is an organic chained calcium and those are ionic.

You do not need to push calcium high while using it. Seachem’s note: it is not necessary to exceed 380 mg/L total calcium with this product, because an uncharged organic molecule costs a coral less energy to take up than a charged ionic one. Corals get as much calcium at a lower number.

Never mix it directly with a carbonate supplement. Seachem’s instruction, not ours: dose the two on alternate days, or at least thirty minutes apart. Excess of one drives the other out of solution, and you end up with a precipitate and two numbers that will not move.

Seachem’s target window for a reef: calcium 380–420 mg/L with alkalinity 3–6 meq/L (8–17 dKH). Make large adjustments slowly — overshooting is easier than correcting, and corals object to the swing more than to the number.

Test with Reef Status: Calcium, which is the kit Seachem write their figures against.

Colour and clarity vary between lots. Seachem say so on the label. A bottle that looks different from your last one is not a bad bottle.

Freshness & Storage

Every batch we dispatch carries a minimum of 6 months’ remaining shelf life. Store this product in a cool, dry place away from direct sunlight, with the cap or inner foil closed tightly after each use.

Returns & Replacement

Returns are accepted within 7 days of delivery, provided the item is unused and in its original packaging. Manufacturer-sealed items cannot be returned once the seal is broken, and sale-priced items are not refundable.

If your item arrives defective or damaged, message us on WhatsApp with your order number, or email us if you would rather, and we will replace it. Approved replacements are delivered within 3 to 5 business days. Transit damage is covered by insurance on every shipment. If tracking shows delivered but nothing reached you, tell us within 72 hours, which is the reporting window Indian couriers allow. Damage caused during installation or use is not covered; replacement spares for such cases are chargeable.

Full terms are on our Cancellation & Returns page.