Seachem Reef Advantage Magnesium 300 gm

Seachem Reef Advantage Magnesium is a concentrated, ionically balanced magnesium source that’s ammonia-free and vital for preventing ionic imbalance.

Reef Advantage Magnesium is a concentrated (80,000 ppm) optimized blend of magnesium, chloride, and salts designed to restore depleted levels of magnesium with minimal impact to the ionic ratios found in natural sea water.

The Seachem Reef Advantage Magnesium 300 gm corrects magnesium, which keeps calcium and KH stable in a reef tank — see our guide to Calcium & Magnesium for how the three interact.

Compatibility

Marine and reef. It contains no ammonia, and the blend of chloride and sulphate salts is chosen so that dosing magnesium does not skew the tank's ionic balance.

Do not mix it directly with a carbonate supplement — dose them on alternate days or at least 30 minutes apart.

Dosage & Directions

Use 5 g (one level teaspoon) for every 80 L (20 US gallons) twice a week, dissolved first in at least a cup of fresh water. Each such dose raises magnesium by about 5 mg/L.

Target 1,200–1,350 mg/L. Do not exceed 25 g per 80 L in a day. Magnesium is the level most often found low in tanks using kalkwasser or heavy carbonate dosing.

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.