Seachem provides dosing instructions on all of our products, so you can always determine the correct dosage, but now it's even easier. With our dosage calculators, just enter a few known values and the calculator does the rest. Add this page to your smartphone home screen for easy access.
Saltwater Planted Sand and Gravel
Reef Advantage Calcium
Water Volume
Units
Current Ca mg/L (ppm)
Desired Ca mg/L (ppm)
To reach your desired level use
g ( tspn)
Do not exceed 10 g/150 L (40 US gallons) per day
Considerations
Use Reef StatusTM Calcium to test calcium levels.
We recommend a Ca level between 380-420 mg/L with an alkalinity between 3-6 meq/L (8-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended levels or shocking corals and inverts. Each 5 g/150 L will raise calcium by about 12 mg/L.
DO NOT OVERDOSE
Do not exceed 10 g/150 L (40 US gallons) per day. Excess calcium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Advantage Magnesium
Water Volume
Units
Current Mg mg/L (ppm)
Desired Mg mg/L (ppm)
To reach your desired level use
g ( tspn)
Do not exceed 25 g/80 L (20 US gallons) per day
Considerations
Use Reef StatusTM Magnesium to test magnesium levels
We recommend a magnesium level between 1200-1350 mg/L. Make large adjustments slowly to avoid overshooting intended level. Amount or frequency can be adjusted, but do not exceed 25 g/80 L per day. Dissolve in at least one cup of freshwater. Excess magnesium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement.
DO NOT OVERDOSE
Do not exceed 25 g/80 L (20 US gallons) per day. Excess magnesium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if magnesium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Advantage Strontium
Water Volume
Units
Current Sr mg/L (ppm)
Desired Sr mg/L (ppm)
To reach your desired level use
g ( tspn)
Considerations
Use Reef StatusTM Strontium to test strontium levels
We recommend a strontium level between 8-12 mg/L. It is advisable to make large adjustments slowly to avoid overshooting intended level. Excess strontium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement.
DO NOT OVERDOSE
Excess strontium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if strontium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Buffer
Water Volume
Units
Current Alkalinity meq/L
Desired Alkalinity meq/L
To reach your desired level use
g ( tspn)
Considerations
Use MultiTestTM Marine pH & Alkalinity to test alkalinity levels.
Reef alkalinity should ideally be maintained at 3-6 meq/L (8-17 dKH). Reef BufferTM will raise carbonate alkalinity; however, it is intended primarily for use as a buffer in a reef system where the maintenance of a pH of 8.3 is often difficult. When pH is not an issue, try Reef BuilderTM or Reef CarbonateTM
DO NOT OVERDOSE
Excess alkalinity may enhance the loss of calcium, magnesium, and strontium. Do not directly mix with any calcium, magnesium, or strontium supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Builder
Water Volume
Units
Current Alkalinity meq/L
Desired Alkalinity meq/L
To reach your desired level use
g ( tspn)
Do not exceed 12 g/150 L (40 US gallons) per day
Considerations
Use MultiTestTM Marine pH & Alkalinity to test alkalinity levels.
Reef alkalinity should ideally be maintained at 3-6 meq/L (8-17 dKH). Alkalinity should not be allowed to fall below 2 meq/L. It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts. Dissolve in at least one cup of freshwater.
DO NOT OVERDOSE
Do not exceed 12 g/150 L (40 US gallons) per day. Excess alkalinity may enhance the loss of calcium, magnesium, and strontium. Do not directly mix with any calcium, magnesium, or strontium supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Calcium
Water Volume
Units
Current Ca mg/L (ppm)
Desired Ca mg/L (ppm)
To reach your desired level use
mL ( caps)
Do not exceed 15 mL per 80 L (20 US gallons) per day
Considerations
Use Reef StatusTM Calcium to test calcium levels.
We recommend a Ca level between 380-420 mg/L with an alkalinity between 3-6 meq/L (8-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts.
DO NOT OVERDOSE
Do not exceed 15 mL per 80 L (20 US gallons) per day. Excess calcium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Carbonate
Water Volume
Units
Current Alkalinity meq/L
Desired Alkalinity meq/L
To reach your desired level use
mL ( caps)
Do not exceed 1 meq/L per day
Considerations
Use MultiTest:TM Marine pH & Alkalinity to measure total alkalinity or Reef StatusTM Magnesium, Carbonate & Borate to measure carbonate alkalinity.
Reef alkalinity should ideally be maintained at 3–6 meq/L (8–17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts. Each dose will raise alkalinity by about 0.25 meq/L.
DO NOT OVERDOSE
Excess alkalinity may enhance the loss of calcium, magnesium, and strontium. Do not directly mix with any calcium, magnesium, or strontium supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Complete
Water Volume
Units
Current Ca mg/L (ppm)
Desired Ca mg/L (ppm)
To reach your desired level use
mL ( caps)
Do not exceed 12.5 mL/80 L (20 US gallons)
Considerations
Use Reef StatusTM Calcium to test calcium levels.
We recommend a Ca level between 380-420 mg/L with an alkalinity between 3-6 meq/L (8-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts.
DO NOT OVERDOSE
Do not exceed 12.5 mL/80 L (20 US gallons). Excess calcium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement. Best if calcium & carbonate additives are added on alternate days or at least 30 minutes apart.
Reef Fusion 1
Water Volume
Units
Current Ca mg/L (ppm)
Desired Ca mg/L (ppm)
To reach your desired level use
mL ( caps)
Do not exceed 4 mL per 25 L (6.5 US gallons) per day
Considerations
Reef FusionTM 1 & 2 are designed to be used together in a 1:1 ratio, but may be used separately to target specific ranges. When using this calculator to calculate a dose for calcium alone, keep in mind that a 1:1 dose with may produce undesired results.
Use Reef StatusTM Calcium to test calcium levels.
We recommend a Ca level between 380-420 mg/L with an alkalinity between 3-6 meq/L (8-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts.
DO NOT OVERDOSE
Do not exceed 4 mL per 25 L (6.5 US gallons) per day.
Reef Fusion 2
Water Volume
Units
Current Alkalinity meq/L
Desired Alkalinity meq/L
To reach your desired level use
mL ( caps)
Do not exceed 4 mL per 25 L (6.5 US gallons) per day
Considerations
Reef FusionTM 1 & 2 are designed to be used together in a 1:1 ratio, but may be used separately to target specific ranges. When using this calculator to calculate a dose for calcium alone, keep in mind that a 1:1 dose with may produce undesired results.
Use MultiTestTM Marine pH & Alkalinity to test alkalinity levels.
We recommend a Ca level between 380-420 mg/L with an alkalinity between 3-6 meq/L (8-17 dKH). It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts.
DO NOT OVERDOSE
Do not exceed 4 mL per 25 L (6.5 US gallons) per day.
Reef Iodide
Water Volume
Units
Current I mg/L (ppm)
Desired I mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations
Use MultiTestTM Iodine & Iodide to test idoide levels.
If necessary, adjust amount so that iodide reads 0.06–0.08 mg/L 6–12 hours after the last dose. Natural seawater has an iodine concentration of .06 mg/L; however, many corals and crustaceans can benefit from a slightly higher concentration. It is normal for iodide levels to decline after a few days. This results from utilization and chemical depletion. Therefore, frequency of use will vary with different reef tanks.
Reef Strontium
Water Volume
Units
Current Sr mg/L (ppm)
Desired Sr mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations
Use Reef StatusTM Strontium to test strontium levels
We recommend a strontium level between 8-12 mg/L. It is advisable to make large adjustments slowly to avoid overshooting intended level. Excess strontium may enhance the loss of carbonate alkalinity. Do not directly mix with any carbonate supplement.
Alkaline Buffer
Water Volume
Units
Current KH meq/L
Desired KH meq/L
To reach your desired level use
grams ( tspns)
Considerations: 2 meq/L is equal to 5.6 dKH. If your test kit measures in dKH, divide your test kit reading by 2.8 to determine your current KH levels in meq/L. Do the same for desired KH.
Equilibrium
Water Volume
Units
Current GH meq/L
Desired GH meq/L
To reach your desired level use
grams ( tbsp)
Considerations: Equilibrium can be added straight, although for optimum solubility we recommend mixing with ~ 1 L (1 qt.) of water (the resulting mixture will have a white opaque appearance). When this mixture is added to the aquarium it will impart a slight haze that should clear within 15–30 minutes.
Flourish
Water Volume
Units
Recommended Dose
mL ( caps)
Considerations: When using in conjunction with Flourish TraceTM, dose on alternate days.
Flourish Iron
Water Volume
Units
Current Fe mg/L (ppm)
Desired Fe mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations: We recommend maintaining an Fe level of about 0.10 mg/L. Iron is used quickly, so you will want to initially exceed 0.10 mg/L in order to prevent iron levels from falling below that level. To accommodate for its quick utilization, the standard of Flourish IronTM dose will raise iron by 0.25 mg/L.
For smaller doses, please note that each cap thread is about 1 mL
Flourish Nitrogen
Water Volume
Units
Current N mg/L (ppm)
Desired N mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations: If using a “nitrate equivalent” value for Current and Desired Nitrogen levels, divide the result by 5.
Flourish Phosphorus
Water Volume
Units
Current P mg/L (ppm)
Desired P mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations: Use once or twice a week or as needed in response to signs of phosphorus deficiency (e.g. stunted growth, plant dark green). The ideal phosphate level will vary, but generally ranges from 0.15–1.0 mg/L. Use MultiTestTM Phosphate to monitor phosphate levels.
Flourish Potassium
Water Volume
Units
Current K mg/L (ppm)
Desired K mg/L (ppm)
To reach your desired level use
mL ( caps)
Considerations: Repeat 2–3 times per week or as needed (in response to signs of potassium deficiency in older leaves which includes: chlorosis (yellowing), necrosis (death/browning), and weak stems and roots.
Flourish Trace
Water Volume
Units
Recommended Dose
mL ( caps)
Considerations: Use twice a week. When using in conjunction with Flourish®, dose on alternate days.
Flourite
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Flourite Black
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Flourite Black Sand
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Flourite Dark
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Flourite Red
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Flourite Sand
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Gray Coast
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
10 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Meridian
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
9 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Onyx
Units
Desired substrate depth
Aquarium width
Aquarium length
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Onyx Sand
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
7 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.
Pearl Beach
Units
Desired substrate depth
Aquarium width
Aquarium length
Your project will require
10 kg bag(s) or 3.5 kg bag(s)
Find a Dealer
Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.
If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth.