Seachem provides dosing instructions on all of our products, so you can always determine the proper amounts to dose, but now we've made it even easier. We've taken our three product lines that normally require some calculation and have done the work for you. Now all you have to do is enter a few known values and the calculator does the rest.

Add this page to your smartphone home screen for easy access.


Saltwater Products


To reach your desired level use:

tspn(s) or grams

For precise dosing, use the
Seachem Digital Spoon Scale

Do not exceed 10 g/150 L (40 US gallons) per day

Considerations: We recommend a Ca level between 380-420 mg/L with an alkalinity between 4-6 meq/L. 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. Quantity or frequency can be adjusted, but do not exceed 10 g/150 L per day.

DO NOT OVERDOSE: 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.

To reach your desired level use:

tspn(s) or grams

For precise dosing, use the
Seachem Digital Spoon Scale

Do not exceed 25 g/80 L (20 US gallons) per day

Considerations: 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.


To reach your desired level use:

tspn(s) or grams

For precise dosing, use the
Seachem Digital Spoon Scale

Make large adjustments slowly to avoid overshooting intended level

Considerations: 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.


To reach your desired level use:

caps or mL

Do not exceed 3 capfuls (15 mL) per 80 L (20 US gallons) per day

Considerations: We recommend a Ca level between 380-420 mg/L with an alkalinity between 4-6 meq/L. It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts.


To reach your desired level use:

caps or mL

Do not exceed 25 mg/L (.25 US gallons) per day

Considerations: We recommend a Ca level between 380-420 mg/L with an alkalinity between 4-6 meq/L. It is advisable to make large adjustments slowly to avoid overshooting intended level or shocking corals and inverts. Each capful will raise calcium by about 10 mg/L. Size or frequency of amount added can be adjusted, but do not exceed 25 mg/L per day.


To reach your desired level use:

tspn(s) or gram(s)

For precise dosing, use the
Seachem Digital Spoon Scale

Considerations: Reef alkalinity should ideally be maintained at 4-5 meq/L (11-14 dKH). Reef Buffer™ 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 Builder™ or Reef Carbonate™


To reach your desired level use:

tspn(s) or gram(s)

For precise dosing, use the
Seachem Digital Spoon Scale

Do not exceed 12 g/150 L (40 US gallons) per day

Considerations: Reef alkalinity should ideally be maintained at 4-5 meq/L (11-17 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.


To reach your desired level use:

caps or mL

Do not exceed 1 meq/L (.25 US gallons) per day.

Considerations: Reef alkalinity should ideally be maintained at 4-5 meq/L (11-17 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.


To reach your desired level use:

caps or mL

Do not exceed a dose of 4 mL per 25 L (6.5 US gallons) per day

Considerations: Reef Fusion 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 a desired calcium value, keep in mind that a 1:1 dose with Reef Fusion 2 may produce undesired results.


To reach your desired level use:

caps or mL

Do not exceed a dose of 4 mL per 25 L (6.5 US gallons) per day

Considerations: Reef Fusion 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 a desired alkalinity value, keep in mind that a 1:1 dose with Reef Fusion 1 may produce undesired results.


To reach your desired level use:

caps or mL

Make large adjustments slowly to avoid overshooting intended level

Considerations: 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.


To reach your desired level use:

caps or mL

Make large adjustments slowly to avoid overshooting intended level

Considerations: 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.

Plant Products


To reach your desired level use:

tspn(s) or gram(s)

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.


To reach your desired level use:

tspn(s) or gram(s)

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.


Recommended dose:

caps or mL

Use Flourish once or twice a week. For smaller doses, please note that each cap thread is approximately 1 mL. Refrigeration after opening is recommended but not required.


To reach your desired level use:

caps or mL

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. For smaller doses, please note that each cap thread is about 1 mL


To reach your desired level use:

caps or mL

Considerations: If using a “nitrate equivalent” value for Current and Desired Nitrogen levels, divide the result by 5.


To reach your desired level use:

caps or mL

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 MultiTest™: Phosphate to monitor phosphate levels.


To reach your desired level use:

caps or mL

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.


Recommended dose:

caps or mL

Sands and Gravels


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

10 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

9 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

7 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.


You require:

10 kg bag(s) or 3.5 kg bag(s)

If you plan on varying the depth of your substrate, use an average depth as your desired substrate depth. Note: The calculator will always round up. For example, you can't purchase 1.3 bags, so it will return 2 bags.