Seachem Reef Fusion 1 500 ml

Seachem Reef Fusion is a highly concentrated two-part calcium and alkalinity system, dosed in a simple 1:1 ratio for stable reef chemistry.

• Provides 100,000 mg/L of ionic calcium.
• Restores and maintains alkalinity.
• Most concentrated two part system; simple 1:1 ratio.

Reef Fusion 1 and Reef Fusion 2 are the foundation of a system formulated to provide the essentials for the reef aquarium. Reef Fusion 1 provides calcium, while Reef Fusion 2 provides alkalinity. When used together, the Reef Fusion system will maintain calcium and alkalinity levels.

Reef Fusion 1

Reef Fusion 1 provides not only 100,000 mg/L of ionic calcium, but also includes biologically appropriate levels of magnesium, strontium, boron, iron, manganese, and molybdenum.

Part of maintaining stable reef chemistry — see our guide to KH (Alkalinity) for why this parameter is tracked closely alongside calcium and magnesium.

Part of maintaining stable reef chemistry — see our guide to Calcium & Magnesium for how this product fits into dosing a reef tank.

Compatibility

Reef aquariums. Seachem item #1203 (500 mL). Reef Fusion 1 is the calcium half of a two-part system; Reef Fusion 2 is the alkalinity half. They are designed to be used together, in a 1:1 ratio.

It provides 100,000 mg/L of ionic calcium — and, unlike a plain calcium chloride solution, biologically appropriate levels of magnesium, strontium, boron, iron, manganese and molybdenum alongside it.

They can be used separately to target one parameter. Seachem allow it, with a caveat worth repeating: if you are correcting calcium alone, a 1:1 dose of both parts may produce a result you did not want. Dose the part you need and test the other.

Not to be mixed with Reef Fusion 2 outside the tank. See the dosing section — this is the one rule the system has.

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.

Dosage & Directions

Dose every one to two days. Shake well first.

1 mL per 25 L (6.5 US gallons), of each part. Add Reef Fusion 1 to a high-current area, wait a few minutes, then add Reef Fusion 2 the same way — shaken, and preferably at a different point in the tank. For reference, the cap holds 5 mL.

That dose contributes 4 mg/L of calcium and 0.176 meq/L of alkalinity. Those two figures are what let you work backwards from a test result to a dose.

Never mix Reef Fusion 1 and Reef Fusion 2 directly. Not in a dosing container, not in a syringe, not in the same spot in the tank. Calcium and carbonate at these concentrations precipitate on contact, and what you get is a cloud of chalk instead of two supplements.

Ceiling: do not exceed 4 mL per 25 L (6.5 US gallons) per day. If the regime is not holding your numbers at that rate, the problem is consumption or a leak in your parameters, not the dose.

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.

Pack Size

A 500 mL bottle.

Seachem make both parts in 500 mL, 1 L, 2 L and 4 L. Buy them in matching sizes. The system is dosed 1:1, so a 2 L bottle of one part and a 500 mL of the other will leave you with three quarters of a bottle you cannot use on its own.

Buy the size you will get through in a reasonable time and keep the bottle closed, cool and out of direct sun. A part-used bottle that has stood open for a year is poorer value than a small fresh one whatever it cost per millilitre.

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.