Reef chemistry reference tool
Reef Dosing Calculator: Daily Consumption & Maintenance Dose
Estimate alkalinity, calcium or magnesium consumption from two comparable test readings, normalize that decline to 24 hours, then scale a daily maintenance dose from the potency printed by your exact supplement manufacturer.
This calculator does not tell you what your target should be, does not contain built-in brand dosing strengths, and is not a one-off correction dose calculator.
Measured-consumption maintenance tool
Estimate a daily maintenance dose from two reef test readings
Use two measurements taken under comparable conditions with no dosing or water changes between the two tests. Then enter the exact potency printed by your supplement manufacturer.
Enter two comparable test results and the potency from your exact supplement label.
What this calculator actually computes
The first step is measured consumption. If alkalinity falls from 8.5 dKH to 8.0 dKH over 24 hours with no dosing or water changes in between, the measured decline is 0.5 dKH/day. A 48-hour interval is normalized to a 24-hour rate rather than treated as one day.
The second step uses label potency. You enter a statement from the exact product instructions such as “X mL raises Y dKH in Z gallons.” The calculator scales that manufacturer-defined strength to your actual system volume and measured daily decline.
Use actual water volume, not only nominal tank size
Rock, sand, operating waterline and sump level can make real water volume different from the aquarium's nominal label. If you need a transparent starting estimate, use the aquarium volume calculator, then refine that estimate when you have better system-specific information.
Any error in water volume directly scales the calculated maintenance amount, so a 20% volume error can produce a roughly 20% dose-scaling error before test and label uncertainty are considered.
Measure consumption before automating it
Test quality matters more than calculator precision. For the three supported parameters, use the relevant comparison guide if you are still choosing a method: reef alkalinity testers, reef calcium testers and reef magnesium testers.
A surprising result should be repeated before it becomes a dosing-program change. Keep the measurement interval as stable as practical: no correction dose, no water change, no major supplement change and no known event that makes the two readings incomparable.
Maintenance dose is not correction dose
This page estimates the amount that would replace the average measured decline. It does not calculate how much product to add to move today's reading to a chosen target.
For a one-time correction, follow the exact product manufacturer instructions, including its stated concentration, mixing procedure, any maximum correction boundary and any requirement to split additions. Retest as instructed before repeating a correction.
Splitting the daily total does not make the schedule universally safe
The “doses per day” field only divides the arithmetic total into equal portions. It does not establish that hourly, four-times-daily or another frequency is chemically appropriate for the exact additive or aquarium.
Once the maintenance amount is justified, our reef dosing methods guide compares two-part, all-in-one, kalkwasser and calcium-reactor control models, while the aquarium dosing pump guide compares calibration evidence, scheduling, channel count and failure boundaries. The pump automates delivery; it still does not decide the chemistry target or dose.
Formula and assumptions
Measured drop = first reading − second reading. Daily consumption = measured drop × 24 ÷ hours between tests. Maintenance dose = daily consumption ÷ label “raises by” value × label dose in mL × system water volume ÷ label reference water volume.
The calculator assumes the two readings describe ordinary consumption over a comparable interval. It does not correct for test error, precipitation, dilution, water changes, manual dosing, kalkwasser/ATO variation, calcium-reactor changes or other simultaneous chemistry inputs. If kalkwasser is the chosen method, the kalkwasser reactor guide covers that hardware decision; if a CO2 reactor is justified, the reef calcium reactor guide covers effluent, monitoring and capacity boundaries.
Methodology and source boundary
PetGearReport has not tested your aquarium, supplement concentration, dosing pump, test-kit repeatability or real delivered volume. This tool performs transparent scaling from numbers you provide. The exact supplement label/current manufacturer instructions remain authoritative for product-specific concentration, compatibility, maximum correction and preparation requirements.
No Amazon price, availability, customer rating or product popularity is used by this calculator.