Seachem Reef Builder 300 g – Reef Aquarium Alkalinity Supplement
Seachem Reef Builder 300 g is a concentrated dry alkalinity supplement formulated specifically for saltwater reef aquariums. It raises carbonate alkalinity, also called KH, with minimal immediate effect on pH, helping replace the carbonates consumed by stony corals, coralline algae, clams, and other calcifying marine organisms.
Reef Builder uses a balanced blend of carbonate sources rather than relying solely on sodium bicarbonate. When used as directed, it raises alkalinity without depleting calcium, magnesium, or strontium, nutrients that can otherwise precipitate when alkalinity is increased improperly.
The 300 g container is well suited for nano, medium, and larger reef aquariums, including SPS, LPS, and mixed reef systems requiring routine alkalinity maintenance.
Key Features
- Raises Carbonate Alkalinity: Replenishes KH consumed by corals, coralline algae, clams, and other calcifying organisms
- Minimal Immediate pH Impact: Designed to raise alkalinity without causing a rapid increase in aquarium pH
- Supports Reef Calcification: Helps maintain carbonate availability needed for coral skeletal growth
- Balanced Carbonate Formula: Uses a blend of carbonate sources that will not lower pH like bicarbonate-only products may
- Protects Ionic Balance: Will not deplete calcium, magnesium, or strontium when used according to the directions
- Suitable for Coral Systems: Ideal for SPS, LPS, mixed reef, and coralline algae aquariums
- Concentrated Dry Formula: Provides economical alkalinity supplementation for regular reef maintenance
- 300 g Container: Convenient for medium to large aquariums or long-term dosing routines
Product Information
- Brand: Seachem
- Product: Reef Builder
- Size: 300 g
- Equivalent Weight: Approximately 10.6 oz
- Product Type: Reef aquarium carbonate alkalinity supplement
- Form: Concentrated dry powder
- Aquarium Type: Saltwater and reef aquariums
- Beginner Dosage: 3 g per 40 US gallons twice weekly
- Effect per Standard Dose: Raises alkalinity by approximately 0.25 meq/L or 0.7 dKH
- Recommended Alkalinity Range: Approximately 3–6 meq/L or 8–17 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
- Correcting low carbonate alkalinity
- Maintaining stable KH between water changes
- Reef aquariums where pH is already within an acceptable range
- Manual or automated alkalinity supplementation routines
Directions for Beginner Use
Use 3 g, approximately one-half level teaspoon, of Seachem Reef Builder for every 40 US gallons of aquarium water twice per week.
Dissolve each dose in at least 250 mL, or one cup, of freshwater before adding it to the aquarium. Once dissolved, slowly add the solution to an area with strong water movement.
Test alkalinity every two weeks when beginning a routine and adjust the amount or frequency according to the aquarium’s measured consumption.
Approximate Beginner Dosage Guide
- 5-Gallon Aquarium: Approximately 0.38 g twice weekly
- 10-Gallon Aquarium: Approximately 0.75 g twice weekly
- 20-Gallon Aquarium: Approximately 1.5 g twice weekly
- 30-Gallon Aquarium: Approximately 2.25 g twice weekly
- 40-Gallon Aquarium: 3 g twice weekly
- 55-Gallon Aquarium: Approximately 4.1 g twice weekly
- 75-Gallon Aquarium: Approximately 5.6 g twice weekly
- 100-Gallon Aquarium: Approximately 7.5 g twice weekly
- 125-Gallon Aquarium: Approximately 9.4 g twice weekly
- 150-Gallon Aquarium: Approximately 11.25 g twice weekly
These amounts are proportional calculations based on Seachem’s standard dose of 3 g per 40 gallons. Calculate the dose from the aquarium’s estimated actual water volume after accounting for rock, sand, equipment, and decorations.
How Much Does Reef Builder Raise Alkalinity?
One standard dose of 3 g per 40 gallons raises alkalinity by approximately 0.25 meq/L.
This is equivalent to approximately 0.7 dKH. Reef Builder is concentrated, but the standard maintenance dose is intentionally moderate to support gradual, stable adjustment.
Do not assume that one-half teaspoon per 40 gallons raises alkalinity by 1 meq/L or 2.8 dKH. A larger increase requires a proportionally larger calculated dose and should be made gradually.
Advanced Dosing
Test aquarium alkalinity before making a correction. Continue using the standard addition regimen until alkalinity reaches the desired range of approximately 3–6 meq/L, equivalent to about 8–17 dKH.
The quantity or dosing frequency may then be adjusted according to the aquarium’s daily or weekly alkalinity consumption.
Do not exceed 12 g per 40 US gallons in one day. Large alkalinity corrections should be divided into smaller additions to reduce the risk of overshooting the target or stressing corals and invertebrates.
Recommended Reef Alkalinity
Seachem recommends maintaining reef aquarium alkalinity between approximately 3 and 6 meq/L, equivalent to about 8–17 dKH. Alkalinity should not be allowed to fall below 2 meq/L.
Many reef aquariums are maintained successfully within a narrower portion of that range. Choose a stable target appropriate for the aquarium’s salt mix, calcium level, nutrient level, coral species, and dosing method.
Consistency is more important than repeatedly chasing one exact number. Rapid alkalinity fluctuations may stress sensitive corals even when every individual test result falls within a technically acceptable range.
How Reef Builder Works
Stony corals, coralline algae, clams, and other calcifying reef organisms use calcium and carbonate to build calcium-carbonate structures. As these organisms grow, carbonate alkalinity is gradually removed from the aquarium water.
Reef Builder replaces carbonate alkalinity and helps maintain the buffering capacity required for stable reef chemistry. It is designed to raise KH without immediately pushing pH sharply upward.
With continued use and appropriate aquarium gas exchange, Reef Builder may contribute to long-term pH stabilization around approximately 8.3.
Reef Builder and pH
Reef Builder is not primarily a pH-adjusting product. It raises carbonate alkalinity with minimal immediate effect on pH.
This makes it useful when alkalinity is low but aquarium pH is already acceptable. When both pH and alkalinity need to be increased, Seachem Reef Buffer may be the more appropriate choice.
Do not continually add Reef Builder solely to correct low pH when alkalinity is already within or above the desired range. Low pH may instead result from elevated indoor carbon dioxide, inadequate aeration, poor surface movement, accumulated organic waste, or inaccurate testing.
Reef Builder vs. Reef Buffer
- Reef Builder: Raises carbonate alkalinity with minimal immediate effect on pH
- Reef Buffer: Raises both carbonate alkalinity and pH
Use Reef Builder when pH is already satisfactory and alkalinity needs to be increased. Use Reef Buffer when both pH and carbonate alkalinity are low.
The two products may be used within the same reef-care routine, but dosing should always be based on current pH and alkalinity test results.
Reef Builder vs. Reef Carbonate
Reef Builder and Reef Carbonate both supply carbonate alkalinity with minimal immediate impact on pH.
- Reef Builder: Concentrated dry powder that must be dissolved before use
- Reef Carbonate: Premixed liquid supplement that may be easier to measure for small or frequent adjustments
Reef Builder generally provides better value for larger systems and reef keepers who prefer concentrated dry supplements. Reef Carbonate may be more convenient for nano tanks, manual dosing, or dosing pumps designed for liquid products.
Using Reef Builder with Calcium Supplements
Reef Builder may be used alongside calcium supplements as part of a balanced reef aquarium routine. However, concentrated carbonate and calcium supplements must never be mixed directly together.
Direct contact can cause calcium carbonate to precipitate, reducing the amount of usable calcium and alkalinity in the aquarium.
Add calcium and carbonate products on alternate days when practical or separate their dosing by at least 30 minutes. Add each product to an area with strong water movement and use separate measuring containers.
Using Reef Builder with Magnesium or Strontium
Do not directly mix Reef Builder with concentrated magnesium or strontium supplements. Dose them on alternate days or separate additions by at least 30 minutes.
When used as directed, Reef Builder is formulated not to deplete calcium, magnesium, or strontium. However, excessive alkalinity can still promote precipitation and loss of these elements.
Maximum Daily Dose
Do not exceed 12 g of Reef Builder per 40 US gallons in one day.
The maximum amount should not be interpreted as a routine daily recommendation. It is an upper safety limit for calculated corrections. Most aquariums require considerably less.
Make significant adjustments slowly and retest before adding more product.
Using Reef Builder in Top-Off Water
Experienced reef keepers may dissolve Reef Builder in freshwater top-off water for gradual addition. The required amount should be based on the aquarium’s measured alkalinity consumption, not merely the volume of evaporated water.
Seachem provides the following formula for calculating the amount to add:
m = 0.08 × v × a
- m: Grams of Reef Builder
- v: Aquarium water volume in liters
- a: Desired alkalinity increase in meq/L
Only plain freshwater evaporates from an aquarium. Alkalinity does not evaporate, so top-off dosing must be matched carefully to actual alkalinity consumption.
Dissolving Reef Builder
Dissolve each dose in at least one cup of freshwater before adding it to the aquarium. Mix thoroughly until the powder is adequately dispersed.
Seachem reports that approximately one teaspoon of Reef Builder can generally be dissolved in about 150 mL of liquid, although results may vary with temperature and preparation method.
Do not pour undissolved powder directly onto corals, live rock, sand, or other aquarium livestock.
Dosing Tips
- Test alkalinity before beginning a dosing routine
- Use a digital gram scale for the most accurate measurement
- Dissolve the powder in freshwater before use
- Add the solution slowly to an area with strong water movement
- Calculate dosing from actual aquarium water volume
- Make large corrections gradually
- Separate Reef Builder from calcium, magnesium, and strontium supplements
- Do not exceed 12 g per 40 gallons in one day
- Keep a written dosing and testing log
- Recalculate consumption as coral colonies grow
Signs Alkalinity May Be Low
- Alkalinity test results declining between water changes
- Difficulty maintaining stable reef pH
- Reduced skeletal growth in stony corals
- Slower coralline algae growth
- Increasing alkalinity consumption as coral colonies grow
Visual symptoms alone cannot confirm low alkalinity. Test with a reliable marine alkalinity kit before changing the dosing schedule.
Important Reef Aquarium Note
Reef Builder raises carbonate alkalinity but does not supply calcium or replace a complete reef supplementation system.
Healthy coral growth also requires suitable calcium, magnesium, salinity, temperature, nutrients, lighting, water flow, and overall aquarium stability.
Excess alkalinity may increase the loss or precipitation of calcium, magnesium, and strontium. Cloudy water or white deposits on heaters, pumps, or aquarium surfaces may indicate precipitation caused by excessive or improperly combined supplementation.
Reef Builder does not replace regular water changes, accurate testing, protein skimmer maintenance, nutrient control, or complete reef aquarium husbandry.
Frequently Asked Questions
What is Seachem Reef Builder used for?
Reef Builder raises and maintains carbonate alkalinity in saltwater reef aquariums with minimal immediate effect on pH.
How much Reef Builder should I use?
The beginner dose is 3 g, or approximately one-half level teaspoon, for every 40 US gallons twice weekly.
How much does the standard dose raise alkalinity?
A 3 g dose per 40 gallons raises alkalinity by approximately 0.25 meq/L, equivalent to about 0.7 dKH.
Does one teaspoon per 40 gallons raise alkalinity by 2.8 dKH?
No. Seachem’s standard dose is one-half teaspoon per 40 gallons, which raises alkalinity by approximately 0.7 dKH.
Does Reef Builder raise pH?
It has minimal immediate effect on pH. With long-term use, it may help stabilize reef aquarium pH around approximately 8.3.
What alkalinity level should I maintain?
Seachem recommends approximately 3–6 meq/L, equivalent to about 8–17 dKH.
What is the difference between Reef Builder and Reef Buffer?
Reef Builder primarily raises alkalinity without significantly increasing pH. Reef Buffer raises both alkalinity and pH.
What is the difference between Reef Builder and Reef Carbonate?
Both raise alkalinity with minimal pH impact. Reef Builder is a concentrated dry powder, while Reef Carbonate is a premixed liquid.
Should Reef Builder be dissolved before use?
Yes. Dissolve each dose in at least one cup of freshwater before adding it to the aquarium.
Can Reef Builder be used with calcium supplements?
Yes, but never mix them directly. Dose them on alternate days or separate additions by at least 30 minutes.
Can Reef Builder be used with magnesium and strontium?
Yes, but concentrated supplements should be added separately and never mixed directly.
Will Reef Builder deplete calcium?
When used as directed, Seachem states that Reef Builder will not deplete calcium, magnesium, or strontium.
Can Reef Builder be overdosed?
Yes. Excess alkalinity may contribute to precipitation and loss of calcium, magnesium, and strontium.
What is the maximum daily dose?
Do not exceed 12 g per 40 US gallons in one day.
Is Reef Builder safe for SPS corals?
Yes, when dosing is based on accurate testing and alkalinity is adjusted gradually.
Can Reef Builder be used in a dosing pump?
It may be dissolved into a properly prepared solution and used with suitable dosing equipment. Keep it separate from calcium, magnesium, and strontium solutions.
Does Reef Builder 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 Builder 300 g provides concentrated carbonate alkalinity supplementation for SPS, LPS, mixed reef, and coralline algae aquariums. Visit Tropical Treasures Wyo in Cheyenne, Wyoming, to shop Seachem reef supplements, calcium and alkalinity test kits, dosing supplies, marine salt, coral foods, and saltwater aquarium care essentials.
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