- Sku: MAG250
- Vendor: Brightwell Aquatics
Brightwell Aquatics Magnesion
Brightwell Magnesion is a concentrated liquid magnesium supplement for reef aquariums. Magnesium is the quiet workhorse of reef chemistry: it keeps calcium and alkalinity in solution so they stay available to your corals instead of precipitating out. Hold it in range alongside Reef Code A and Reef Code B, and browse more Brightwell Aquatics reef care.
Why Magnesium Matters
Natural seawater holds magnesium at about 1,290 to 1,320 ppm, roughly three times the level of calcium. At that concentration it stops calcium and carbonate from bonding and falling out of solution. If magnesium drifts low, dosing calcium and alkalinity becomes inefficient, your numbers get hard to hold, and precipitation can cloud the water or coat your equipment. Keeping magnesium in range is what makes the rest of your dosing work.
Features
- Concentrated liquid magnesium for marine and reef aquariums
- Keeps calcium and alkalinity stable and available to corals
- Each ml raises magnesium in 1 gallon by about 26 ppm
- Reef safe, with no phosphate or nitrate
Directions for Use
Shake well before use and test your magnesium before dosing. For maintenance, add 5 ml (1 capful) per 20 gallons every other day, or as needed, to hold magnesium between 1,290 and 1,320 ppm. Each ml raises magnesium in 1 gallon by about 26 ppm. If magnesium is below 1,288 ppm, you can dose up to 10 ml per 20 gallons daily until it reaches your target, then return to maintenance dosing. Used for maintenance, 250 ml treats up to 1,000 gallons.
Choose Your Size
| Size | Best for |
|---|---|
| 250 ml | Nano and smaller reef tanks, or occasional magnesium top-ups. |
| 500 ml | Mid-size reef tanks on a regular dosing schedule. |
| 2 L | Larger or coral-heavy systems, with the best value per ml. |
Specifications
| Brand | Brightwell Aquatics |
| Product | Magnesion, liquid magnesium supplement |
| Raises | About 26 ppm magnesium per ml, per gallon |
| Target range | 1,290 to 1,320 ppm magnesium |
| Use with | Reef Code A and Reef Code B |
| Best for | Saltwater reef aquariums |
| Available sizes | 250 ml, 500 ml, 2 L |
| Reef safe | Yes |
| Country of origin | United States |
Recommended Pairings
- Reef Code A supplies calcium in the balanced two-part system.
- Reef Code B supplies alkalinity in the balanced two-part system.
- Brightwell Aquatics is the full brand lineup.
- Additives and supplements for more reef dosing options.
FAQ
Why do I need to dose magnesium? Magnesium keeps calcium and carbonate in solution. Without enough of it, dosing calcium and alkalinity becomes a losing battle because they precipitate out instead of feeding your corals. Correct magnesium makes your calcium and alkalinity dosing stable and efficient.
How often should I test magnesium? Magnesium moves more slowly than calcium and alkalinity, so testing every week or two is usually enough for an established tank. Test before dosing and adjust to keep it in the 1,290 to 1,320 ppm range.
Is Magnesion reef safe? Yes. It is formulated for reef aquariums and is safe for corals and other invertebrates when dosed to your test results.
How much will one dose raise my magnesium? Each ml raises magnesium in 1 gallon by about 26 ppm, so a 5 ml dose per 20 gallons nudges it up gradually. Correct low magnesium slowly rather than all at once.
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Brightwell Aquatics Magnesion
