Seachem Reef Fusion 2 500 mL – Two-Part Reef Alkalinity Supplement
Seachem Reef Fusion 2 500 mL is the alkalinity component of Seachem’s concentrated two-part Reef Fusion system. It supplies carbonate and bicarbonate alkalinity needed by stony corals, coralline algae, clams, and other calcifying reef organisms.
When used with Seachem Reef Fusion 1, Reef Fusion 2 provides balanced calcium and alkalinity supplementation in a convenient 1:1 dosing ratio. Reef Fusion 1 supplies calcium and supporting elements, while Reef Fusion 2 replaces the alkalinity consumed during coral skeletal growth and reef calcification.
The concentrated liquid formula is suitable for manual dosing or automated dosing systems. The 500 mL bottle is ideal for nano, small, and medium reef aquariums or for reef keepers beginning a consistent two-part supplementation routine.
Key Features
- Concentrated Alkalinity Supplement: Supplies carbonate and bicarbonate alkalinity for reef aquariums
- Part Two of the Reef Fusion System: Designed for use with calcium-rich Seachem Reef Fusion 1
- Simple 1:1 Dosing Ratio: Normally dosed in equal quantities with Reef Fusion 1
- Supports Reef Calcification: Replenishes alkalinity used during coral skeletal growth
- Helps Maintain pH Stability: Adequate alkalinity helps aquarium water resist rapid downward pH changes
- Independent Correction Option: May be dosed separately when alkalinity is low but calcium is already within range
- Manual or Automated Dosing: Suitable for hand dosing or a properly configured aquarium dosing pump
- Convenient 500 mL Bottle: Well suited for nano, small, and medium reef aquarium systems
Product Information
- Brand: Seachem
- Product: Reef Fusion 2
- Size: 500 mL
- Equivalent Size: Approximately 17 fl oz
- Product Type: Concentrated reef aquarium alkalinity supplement
- System: Part two of the Seachem Reef Fusion two-part system
- Primary Function: Replenishes carbonate and bicarbonate alkalinity
- Aquarium Type: Saltwater and reef aquariums
- Standard Dosage: 1 mL per 6.5 US gallons every one to two days
- Alkalinity Added per Standard Dose: Approximately 0.176 meq/L or 0.5 dKH
Best Used For
- SPS coral aquariums
- LPS coral aquariums
- Mixed reef systems
- Reef aquariums with growing coral colonies
- Systems with active coralline algae growth
- Marine aquariums containing clams
- Maintaining carbonate alkalinity between water changes
- Correcting low alkalinity independently from calcium
- Manual two-part reef dosing
- Automated aquarium dosing systems
Standard Directions
Shake Seachem Reef Fusion 2 well before use.
Add 1 mL of Reef Fusion 1 for every 6.5 US gallons of aquarium water. Add Reef Fusion 1 to an area with strong water movement and allow it to disperse for several minutes.
Then add the same amount of Reef Fusion 2 to a separate high-flow area of the aquarium. Dose the aquarium every one to two days and adjust the amount or frequency according to calcium and alkalinity testing.
Never mix concentrated Reef Fusion 1 and Reef Fusion 2 directly in the same container, dosing reservoir, measuring cup, tubing, or pump channel.
Approximate Standard Dosage Guide
- 5-Gallon Aquarium: Approximately 0.8 mL every one to two days
- 10-Gallon Aquarium: Approximately 1.5 mL every one to two days
- 20-Gallon Aquarium: Approximately 3.1 mL every one to two days
- 30-Gallon Aquarium: Approximately 4.6 mL every one to two days
- 40-Gallon Aquarium: Approximately 6.2 mL every one to two days
- 55-Gallon Aquarium: Approximately 8.5 mL every one to two days
- 75-Gallon Aquarium: Approximately 11.5 mL every one to two days
- 100-Gallon Aquarium: Approximately 15.4 mL every one to two days
- 125-Gallon Aquarium: Approximately 19.2 mL every one to two days
- 150-Gallon Aquarium: Approximately 23.1 mL every one to two days
These amounts are proportional calculations based on Seachem’s standard dosage. Calculate the dose using the aquarium’s estimated actual water volume after accounting for live rock, sand, decorations, sump equipment, and other displacement.
How Much Alkalinity Does One Dose Add?
The standard dose of 1 mL per 6.5 gallons contributes approximately 0.176 meq/L of alkalinity.
This is equivalent to approximately 0.5 dKH. The standard dose is designed for ongoing supplementation rather than a large one-time alkalinity correction.
One milliliter per 25 gallons would add substantially less than 0.5 dKH and is not Seachem’s official standard dose.
Recommended Alkalinity Range
Seachem recommends maintaining reef aquarium alkalinity between approximately 3 and 6 meq/L, equivalent to about 8–17 dKH.
Calcium should generally be maintained between approximately 380 and 420 mg/L while using the Reef Fusion system.
Many reef aquariums are maintained within a narrower portion of these ranges. Select stable targets appropriate for the aquarium’s coral species, nutrient levels, salt mix, and supplementation method.
Parameter stability is generally more important than repeatedly chasing one exact value. Rapid alkalinity fluctuations can stress sensitive corals even when the final measurement falls within an acceptable range.
How Reef Fusion 2 Works
Stony corals, coralline algae, clams, and other calcifying reef organisms combine calcium with carbonate to form calcium-carbonate structures.
As these organisms grow, both calcium and carbonate alkalinity are consumed. Reef Fusion 1 replaces calcium, while Reef Fusion 2 replaces the carbonate and bicarbonate alkalinity used during calcification.
Using both products in equal amounts helps replace calcium and alkalinity in a balanced ratio when the aquarium is consuming them proportionally.
Using Reef Fusion 1 and Reef Fusion 2 Together
Reef Fusion 1 and Reef Fusion 2 are designed to be used in a 1:1 ratio. For example, an aquarium receiving 5 mL of Reef Fusion 1 would normally receive 5 mL of Reef Fusion 2.
Add Reef Fusion 1 first, allow several minutes for it to disperse, and then add Reef Fusion 2. Whenever practical, dose the products in separate high-flow areas.
Never combine the concentrates directly. Concentrated calcium and carbonate can react and form insoluble calcium carbonate, reducing the amount of usable calcium and alkalinity reaching the aquarium.
Can Reef Fusion 2 Be Used Separately?
Yes. Reef Fusion 2 may be used independently when alkalinity is below the desired range but calcium is already correct.
Similarly, Reef Fusion 1 may be used separately when calcium is low but alkalinity is already within range.
Once the parameters have been corrected and balanced, equal dosing may resume based on the aquarium’s ongoing consumption.
Always test both calcium and alkalinity before making an independent correction. Automatically adding equal amounts to an imbalanced aquarium may cause one parameter to rise beyond the desired range.
Maximum Daily Dose
Do not exceed 4 mL of Reef Fusion 2 per 6.5 US gallons in one day.
The maximum amount is an upper dosing limit and should not be treated as a normal daily recommendation. Most reef aquariums require considerably less.
Make large alkalinity corrections gradually. Retest before adding another correction and avoid abruptly changing aquarium chemistry.
Using Reef Fusion 2 with a Dosing Pump
Reef Fusion 2 may be dispensed through an automated dosing pump. It must have its own dedicated reservoir, pump channel, tubing, and outlet.
Do not share a dosing line or reservoir with Reef Fusion 1. Program the two products to dispense at different times or into separate high-flow locations.
Determine the aquarium’s average daily consumption before programming a permanent schedule. Test alkalinity at approximately the same time each day for several days, calculate the average decline, and then adjust the daily dose to replace that amount.
Dividing the required daily dose into several smaller additions may improve stability in heavily stocked SPS or mixed reef systems.
Reef Fusion 2 vs. Reef Carbonate
Both products raise carbonate alkalinity, but they are intended for different supplementation approaches.
- Reef Fusion 2: The alkalinity component of a balanced two-part system, normally paired in equal amounts with Reef Fusion 1
- Reef Carbonate: A standalone liquid alkalinity supplement used independently according to measured KH demand
Reef Fusion 2 is convenient when calcium and alkalinity are being consumed proportionally. Reef Carbonate may be preferable when alkalinity needs to be managed separately as part of another calcium-supplementation routine.
Reef Fusion 2 vs. Reef Builder
Reef Fusion 2 and Reef Builder both replenish alkalinity but differ in form and intended dosing system.
- Reef Fusion 2: Concentrated liquid designed to pair with Reef Fusion 1
- Reef Builder: Concentrated dry alkalinity supplement that must be dissolved before use
Reef Fusion 2 offers the convenience of a ready-to-dose liquid and balanced two-part supplementation. Reef Builder may provide greater economy for larger systems or aquarists who prefer dry additives.
Reef Fusion 2 and pH
Carbonate alkalinity helps aquarium water resist downward pH changes. Maintaining adequate alkalinity can therefore support reef aquarium pH stability.
However, Reef Fusion 2 should not be used solely to chase a higher pH when alkalinity is already within or above the desired range.
Persistently low pH may be associated with elevated indoor carbon dioxide, inadequate aeration, weak surface movement, accumulated organic waste, or inaccurate testing. These underlying conditions should be investigated before increasing alkalinity unnecessarily.
Dosing Tips
- Shake the bottle before each use
- Test calcium and alkalinity before starting a dosing routine
- Calculate dosage using actual aquarium water volume
- Add Reef Fusion 1 and Reef Fusion 2 separately
- Wait several minutes between the two products
- Dose into separate high-flow areas whenever practical
- Never mix the concentrated products directly
- Use dedicated dosing-pump reservoirs, tubing, and channels
- Make significant alkalinity corrections gradually
- Keep a written testing and dosing log
Signs Alkalinity May Be Low
- Declining alkalinity test results between water changes
- Difficulty maintaining stable reef aquarium pH
- Reduced skeletal growth in SPS or LPS corals
- Slower coralline algae development
- Increasing alkalinity consumption as coral colonies grow
- Alkalinity repeatedly falling below the selected target
Visual symptoms alone cannot confirm low alkalinity. Poor coral growth, reduced polyp extension, faded coloration, or tissue loss may also result from unstable salinity, temperature changes, nutrient imbalance, lighting, pests, disease, or insufficient water flow.
Important Reef Aquarium Note
Reef Fusion 2 supplies alkalinity but does not provide calcium. It is normally paired with Reef Fusion 1 to create a balanced two-part supplementation system.
Healthy reef growth depends on stable alkalinity, calcium, magnesium, salinity, temperature, nutrients, lighting, water flow, and overall aquarium maturity.
Excess alkalinity may promote calcium-carbonate precipitation. Cloudy water or white deposits on pumps, heaters, and aquarium surfaces may indicate excessive dosing or direct contact between concentrated calcium and alkalinity supplements.
Reef Fusion 2 does not replace regular water changes, accurate testing, protein-skimmer maintenance, nutrient management, or complete reef aquarium husbandry.
Frequently Asked Questions
What is Seachem Reef Fusion 2 used for?
Reef Fusion 2 supplies carbonate and bicarbonate alkalinity for coral skeletal growth, reef calcification, and aquarium buffering stability.
Is Reef Fusion 2 calcium or alkalinity?
Reef Fusion 2 is the alkalinity component. Reef Fusion 1 is the calcium component.
How much Reef Fusion 2 should I use?
Use 1 mL for every 6.5 US gallons every one to two days, then adjust according to testing and aquarium demand.
How much alkalinity does the standard dose add?
The standard dose contributes approximately 0.176 meq/L, equivalent to about 0.5 dKH.
Does 1 mL per 25 gallons raise alkalinity by 0.5 dKH?
No. The official dose that raises alkalinity by approximately 0.5 dKH is 1 mL per 6.5 gallons.
Do I need Reef Fusion 1?
Reef Fusion 1 and 2 are designed to be used together when calcium and alkalinity are being consumed proportionally. Reef Fusion 2 may also be used separately to correct low alkalinity.
Should Reef Fusion 1 and Reef Fusion 2 be dosed equally?
Yes, they are normally used in a 1:1 ratio once calcium and alkalinity are balanced.
Can Reef Fusion 2 be used without Reef Fusion 1?
Yes. It may be used independently when alkalinity is low but calcium is already within the desired range.
Can Reef Fusion 1 and 2 be mixed together?
No. Never mix the concentrated products directly. Add them separately and wait several minutes between doses.
Where should Reef Fusion 2 be added?
Add it to an area with strong water movement, preferably separate from the location used for Reef Fusion 1.
What alkalinity level should I maintain?
Seachem recommends approximately 3–6 meq/L, equivalent to about 8–17 dKH.
What is the maximum daily dose?
Do not exceed 4 mL per 6.5 gallons in one day.
Does Reef Fusion 2 raise pH?
Maintaining adequate alkalinity supports pH stability, but Reef Fusion 2 should not be used solely to chase pH when alkalinity is already adequate.
What is the difference between Reef Fusion 2 and Reef Carbonate?
Reef Fusion 2 is part of a balanced two-part system. Reef Carbonate is a standalone liquid alkalinity supplement.
Can Reef Fusion 2 be used with a dosing pump?
Yes. Use a dedicated reservoir, pump channel, tubing, and outlet separate from Reef Fusion 1.
Is Reef Fusion 2 safe for SPS corals?
Yes, when dosing is based on accurate testing and alkalinity is adjusted gradually.
Can alkalinity be overdosed?
Yes. Excess alkalinity can stress corals and cause calcium-carbonate precipitation.
Does Reef Fusion 2 replace water changes?
No. It replenishes alkalinity but does not replace water changes, testing, nutrient management, or complete reef aquarium maintenance.
Available at Tropical Treasures Wyo
Seachem Reef Fusion 2 500 mL provides concentrated carbonate and bicarbonate alkalinity for SPS, LPS, mixed reef, and coralline algae aquariums. Pair it with Seachem Reef Fusion 1 for a balanced two-part calcium and alkalinity supplementation system.
Visit Tropical Treasures Wyo in Cheyenne, Wyoming, to shop Seachem reef supplements, calcium and alkalinity test kits, dosing pumps, marine salt, coral foods, and saltwater aquarium care essentials.
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