Red Sea Marine Care Magnesium Test Kit
Red Sea Marine Care Magnesium Test Kit
The element that keeps calcium and alkalinity honest. The Red Sea Marine Care Magnesium Test Kit measures magnesium in marine and reef aquariums by titration — a precise syringe drop-count read straight off the syringe barrel. Magnesium sits quietly in the background of every calcium and alkalinity swing; when either won't hold steady, magnesium is usually the reason.
Key features
- 75 titration tests per kit — magnesium moves slowly, so this typically lasts well over a year of monthly testing.
- Selectable resolution — 100 ppm for a fast check, 50 ppm when you need to confirm a dosing change landed.
- Titration method — dose reagent by the drop with the supplied 5 mL syringe until the colour changes; the drop count is the reading.
- Conversion chart included — reads the drop count straight to ppm.
Specifications
| Property | Value |
|---|---|
| Measures | Magnesium (Mg) |
| Method | Titration (syringe drop-count) |
| Resolution | Selectable 50 ppm or 100 ppm |
| Tests per kit | 75 |
| Water type | Marine and reef |
| Storage | Sealed, 15–25°C, use before the expiry date printed on the pack |
What's included / Not included
The kit includes Reagent A (15 mL), Reagent B (15 mL), Reagent C (50 mL), a 5 mL syringe, a glass test vial and printed instructions with a colour reference card — everything needed for 75 tests. It does not include a calcium or alkalinity test; those are separate kits, best run alongside this one rather than in isolation.
Suitable for, and not suitable for
Suitable for any marine or reef system, and most useful in mixed reef and SPS tanks where calcium and alkalinity are being dosed regularly. Less critical on a fish-only tank with no calcifying livestock, where magnesium rarely drifts.
Target ranges
| System type | Target magnesium |
|---|---|
| FOWLR (fish only with live rock) | 1,250–1,350 mg/L |
| Mixed reef / soft and LPS coral | 1,300–1,400 mg/L |
| SPS-dominated reef | 1,300–1,400 mg/L, held alongside calcium 420–450 mg/L and alkalinity 7–9 dKH |
These are marine and reef target ranges. Magnesium is not a parameter tracked in freshwater community, planted or African cichlid tanks, so no freshwater target range applies to this kit.
What to do when the reading is out of range
Low magnesium is corrected with a magnesium supplement such as Red Sea Reef Care Magnesium Foundation C. Raise it gradually rather than in one large dose, and retest a few days later rather than immediately — magnesium takes time to fully equilibrate through the water column.
Care and storage
Keep sealed, store between 15–25°C out of direct sun, and check the expiry date printed on the pack before trusting an older kit's result.
Warranty and delivery
Covered by the consumer guarantees under Australian Consumer Law, in addition to any manufacturer undertaking. Standard parcel freight — no special handling required.
Goes well with
- Red Sea Marine Care Calcium Test Kit — test together; magnesium stabilises calcium.
- Red Sea KH/Alkalinity Pro Testing Kit — the third leg of the calcium/alkalinity/magnesium triangle.
- Red Sea Reef Care Magnesium Foundation C — the matching dosing solution when magnesium reads low.
Common questions
Why does low magnesium affect calcium and alkalinity?
Magnesium keeps calcium and carbonate in solution at reef-tank concentrations. When magnesium is low, calcium and alkalinity become harder to raise and hold — dosing either one just gets consumed faster or precipitates out.
How often should I test magnesium?
Monthly is enough for most tanks — it moves far more slowly than calcium or alkalinity.
My calcium and alkalinity won't hold steady even though I'm dosing correctly — what should I check?
Test magnesium. A low reading is the most common hidden cause of calcium and alkalinity instability in an otherwise well-dosed tank.
Is this the same as the Magnesium Pro test kit?
No — this is the Marine Care tier, calibrated to 50 or 100 ppm resolution. Red Sea's Magnesium Pro kit is a separate, higher-resolution product for reef keepers chasing tighter control.
