Brightwell Aquatics Magnesion 500 mL – Reef Aquarium Magnesium Supplement
Brightwell Aquatics Magnesion 500 mL is a highly concentrated ionic magnesium supplement formulated for marine and reef aquariums. It helps establish and maintain magnesium within the natural seawater range while supporting balanced calcium, alkalinity, and carbonate chemistry.
Magnesium plays an important role in reef aquarium stability. Adequate magnesium helps reduce unwanted calcium-carbonate precipitation, allowing calcium and alkalinity to remain more readily available to corals, clams, coralline algae, and other reef-building organisms.
Magnesion contains no unwanted organic complexing agents such as EDTA, gluconate, or polygluconate. Its concentrated liquid formula is easy to measure for routine maintenance or controlled correction of a tested magnesium deficiency.
Key Features
- Concentrated Ionic Magnesium: Raises magnesium in marine and reef aquariums
- Supports Reef Chemistry: Helps regulate the balance between calcium and carbonates
- Supports Calcification: Magnesium is incorporated into aragonite produced by corals, clams, and other reef-building organisms
- Helps Limit Precipitation: Proper magnesium levels help keep calcium and carbonate available in aquarium water
- No Organic Complexing Agents: Contains no EDTA, gluconate, or polygluconate
- Test-Based Dosing: Suitable for routine maintenance and controlled magnesium correction
- Marine & Reef Formula: Intended for saltwater aquariums
- Large 500 mL Size: Treats up to approximately 2,000 cumulative gallons at the basic dose
Product Details
- Brand: Brightwell Aquatics
- Product: Magnesion
- Size: 500 mL
- Equivalent Size: Approximately 16.9 fl oz
- Product Type: Ionic magnesium supplement
- Aquarium Type: Marine and reef aquariums
- Recommended Magnesium Range: 1,290–1,320 ppm
- Basic Dose: 5 mL per 20 US gallons every other day
- Maximum Correction Dose: 10 mL per 20 US gallons daily
- Concentration: 1 mL raises magnesium by approximately 26 ppm in 1 US gallon
Best Used For
- Reef aquariums with tested magnesium deficiencies
- SPS, LPS, soft-coral, and mixed reef systems
- Marine aquariums containing clams or coralline algae
- Maintaining magnesium near natural seawater levels
- Supporting calcium and alkalinity stability
- Replacing magnesium consumed between water changes
- Correcting low magnesium gradually
- Systems using calcium and alkalinity supplements
Why Magnesium Matters
Magnesium is one of the major ions found in seawater. It helps regulate interactions between calcium and carbonate and reduces the tendency of these ions to precipitate prematurely as calcium carbonate.
When magnesium is too low, aquarists may have difficulty maintaining calcium and alkalinity even when those supplements are being added regularly. Correcting the magnesium deficiency may make the overall reef supplementation program easier to stabilize.
Magnesium is also incorporated into aragonite, the mineral structure produced by stony corals, clams, coralline algae, and other calcifying marine organisms.
Basic Directions
Shake the bottle well before each use.
Add:
5 mL per 20 US gallons every other day, or as needed to maintain magnesium between 1,290 and 1,320 ppm.
Test magnesium regularly and adjust the frequency according to the aquarium’s actual rate of consumption.
Basic Dosage Guide
- 10 Gallons: Approximately 2.5 mL every other day
- 20 Gallons: 5 mL every other day
- 40 Gallons: 10 mL every other day
- 50 Gallons: Approximately 12.5 mL every other day
- 55 Gallons: Approximately 13.75 mL every other day
- 75 Gallons: Approximately 18.75 mL every other day
- 100 Gallons: 25 mL every other day
- 125 Gallons: Approximately 31.25 mL every other day
- 150 Gallons: Approximately 37.5 mL every other day
- 200 Gallons: 50 mL every other day
These amounts are the manufacturer’s basic maintenance doses. Do not dose automatically if magnesium is already within or above the desired range.
Correcting Low Magnesium
Determine the aquarium’s magnesium concentration with an accurate marine magnesium test before dosing.
If magnesium is below approximately 1,288 ppm, Magnesion may be added at a maximum rate of:
10 mL per 20 US gallons daily.
Continue testing and stop corrective dosing when the desired concentration is reached. After correction, switch to a smaller daily or weekly maintenance amount based on the aquarium’s measured consumption.
Do not exceed the maximum correction rate. Raising magnesium gradually reduces the risk of sudden changes in salinity and ionic balance.
Advanced Dosing Formula
Each 1 mL of Magnesion raises magnesium by approximately 26 ppm in 1 US gallon of aquarium water.
Use the following formula:
Required mL = Aquarium gallons × desired magnesium increase ÷ 26
Example
To raise magnesium by 50 ppm in a 100-gallon system:
100 × 50 ÷ 26 = approximately 192 mL total
This total amount should not be added all at once. The maximum daily dose for a 100-gallon aquarium is 50 mL, so the correction should be divided across several days while magnesium is tested regularly.
Approximate Dose Needed to Raise Magnesium by 10 ppm
- 20 Gallons: Approximately 7.7 mL
- 40 Gallons: Approximately 15.4 mL
- 50 Gallons: Approximately 19.2 mL
- 75 Gallons: Approximately 28.8 mL
- 100 Gallons: Approximately 38.5 mL
- 125 Gallons: Approximately 48.1 mL
- 150 Gallons: Approximately 57.7 mL
- 200 Gallons: Approximately 76.9 mL
Calculate dosage from the aquarium’s actual water volume after accounting for displacement from rock, sand, and equipment.
Determining the Maintenance Dose
After reaching the desired magnesium level, measure magnesium at approximately the same time each day for one to two weeks.
Calculate the average daily decrease, then use this formula:
Daily dose in mL = Aquarium gallons × daily magnesium decrease ÷ 26
Smaller daily additions generally maintain a more stable magnesium concentration than occasional large corrections.
How Much Does the 500 mL Bottle Treat?
At the basic dosage of 5 mL per 20 gallons:
A 500 mL bottle provides approximately 100 standard doses and treats up to 2,000 cumulative gallons.
Examples include:
- Approximately 100 basic doses for a 20-gallon aquarium
- Approximately 50 basic doses for a 40-gallon aquarium
- Approximately 20 basic doses for a 100-gallon aquarium
Actual product life depends on aquarium size, starting magnesium concentration, water-change schedule, salt mix, and magnesium demand.
Using Magnesion with Calcium and Alkalinity Supplements
Magnesion may be used as part of a reef supplementation program that also includes calcium and alkalinity products.
Test each parameter separately because calcium, alkalinity, and magnesium are consumed at different rates. Do not assume equal amounts of all three supplements will be required.
Add concentrated supplements separately into an area of strong water movement. Do not mix Magnesion directly with calcium or alkalinity concentrates in the same dosing container unless the product manufacturer specifically allows it.
Using Magnesion with Water Changes
A quality marine salt mix should establish magnesium near the desired seawater range. Test newly mixed saltwater before adding additional magnesium because salt mixes vary in concentration.
Regular water changes may replace part or all of the magnesium consumed by lightly stocked systems. Heavily stocked reef aquariums may require additional supplementation between water changes.
Magnesion vs. Hydrāt-Mg
- Magnesion: Intended primarily to establish and maintain magnesium near the natural seawater range of 1,290–1,320 ppm
- Hydrāt-Mg: A separate Brightwell formula that may be used by experienced aquarists when intentionally maintaining magnesium at substantially elevated concentrations
Most reef aquariums should maintain magnesium near the range recommended for Magnesion rather than intentionally raising it far above natural seawater levels.
Does Magnesion Directly Grow Corals?
Magnesion supplies magnesium, an important component of stable reef chemistry and aragonite formation. However, it does not directly guarantee coral growth, coloration, or recovery.
Coral growth also depends on:
- Stable alkalinity
- Adequate calcium
- Appropriate lighting
- Balanced nitrate and phosphate
- Suitable water flow
- Stable salinity and temperature
- Feeding and trace-element availability
- Freedom from pests and disease
Important Testing Guidance
Always test magnesium before attempting a correction. Unexpected results may come from an inaccurate test, incorrect saltwater volume, or errors in test procedure.
For reliable results:
- Use a quality marine magnesium test
- Follow the test instructions precisely
- Confirm unusual readings before adding a large dose
- Calculate from actual system water volume
- Retest during multi-day corrections
- Monitor calcium, alkalinity, and salinity alongside magnesium
Can Magnesion Be Overdosed?
Yes. Excessive magnesium supplementation can disrupt the aquarium’s ionic balance and increase salinity.
Do not add Magnesion simply because calcium or alkalinity is difficult to maintain. First confirm that magnesium is actually below the desired range.
If an excessive amount is added, stop dosing, verify magnesium and salinity, and perform gradual water changes with correctly mixed saltwater if necessary.
Frequently Asked Questions
What is Brightwell Magnesion used for?
It raises and maintains magnesium in marine and reef aquariums while supporting balanced calcium and carbonate chemistry.
What magnesium level does Brightwell recommend?
Brightwell recommends maintaining magnesium between approximately 1,290 and 1,320 ppm.
What is the basic dose?
Add 5 mL per 20 gallons every other day or as needed based on testing.
How much does 1 mL raise magnesium?
One milliliter raises magnesium by approximately 26 ppm in 1 gallon of water.
What is the maximum daily correction dose?
Do not exceed 10 mL per 20 gallons daily.
How much does the 500 mL bottle treat?
At the basic dose, it treats up to approximately 2,000 cumulative gallons.
Why is magnesium important in reef aquariums?
Magnesium helps regulate calcium and carbonate interactions and reduces unwanted calcium-carbonate precipitation.
Does Magnesion raise calcium or alkalinity?
No. It is a magnesium-specific supplement. Calcium and alkalinity should be tested and supplemented separately when required.
Can it be used with calcium and alkalinity supplements?
Yes. Dose each product separately and adjust each one according to its respective test result.
Is Magnesion reef safe?
Yes, when used as directed and dosed according to accurate magnesium testing.
Will Magnesion prevent all calcium precipitation?
No. Proper magnesium helps reduce premature precipitation, but excessively high pH, calcium, or alkalinity can still cause calcium carbonate to precipitate.
Does Magnesion contain EDTA?
No. Brightwell states that it contains no unwanted organic material such as EDTA, gluconate, or polygluconate.
Can I dose Magnesion automatically?
Yes, after determining the aquarium’s actual daily magnesium consumption and accurately calibrating the dosing pump.
Is Magnesion suitable for freshwater aquariums?
No. It is formulated for marine and reef aquarium chemistry.
Does Magnesion replace water changes?
No. It supplements magnesium but does not remove waste or replace routine aquarium maintenance.
Available at Tropical Treasures Wyo
Brightwell Aquatics Magnesion 500 mL provides concentrated ionic magnesium for maintaining stable reef aquarium chemistry near natural seawater levels.
Visit Tropical Treasures Wyo in Cheyenne, Wyoming, to shop Brightwell Aquatics Magnesion, marine magnesium tests, calcium and alkalinity supplements, reef salt mixes, dosing equipment, and other saltwater aquarium supplies.
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