Coral Compass Pro · $3/month · what's included
Enter two or more dated alkalinity and calcium tests and your current daily dose. The planner fits a trend line through your tests to measure how fast your corals actually consume alkalinity and calcium, then gives the daily dose that holds both steady and a schedule split across your doser's time slots, with alk and calcium offset so they never go in together. It also checks your calcium-to-alkalinity consumption ratio against theory (about 20 ppm calcium per meq/L of alkalinity), which catches bad tests early. Pro subscribers can load tests straight from a saved tank.
The math
Consumption (dKH/day) = alk added per day − trend slope
Alk added per day = mL/day × 1.4 ÷ gallons (Recipe 1)
Hold-steady dose = consumption × gallons ÷ 1.4
Calcium uses 10 ppm per mL per gallon. Upward corrections are limited to 0.5 dKH per day on top of the maintenance dose.
Try it
Sample: 100 gal, dosing 100 mL/day of each part, three tests over a week (8.5 → 8.0 dKH, 430 → 425 ppm).
Alkalinity consumption: 1.47 dKH/day. Hold-steady dose: 105.1 mL/day alk and 107.2 mL/day calcium. Ca used per meq/L alk: 20.4 ppm (theory 20.0).
| Time | Alk | Time | Calcium |
|---|---|---|---|
| 00:00 | 26.28 mL | 03:00 | 26.79 mL |
| 06:00 | 26.28 mL | 09:00 | 26.79 mL |
| 12:00 | 26.28 mL | 15:00 | 26.79 mL |
| 18:00 | 26.28 mL | 21:00 | 26.79 mL |
Sources
- Randy Holmes-Farley, "Solving Calcium and Alkalinity Problems" and the "Recipe 1" two-part (Reefkeeping Magazine): 1 mL per US gallon raises alkalinity about 1.4 dKH and calcium about 10 ppm
- Calcium carbonate stoichiometry: 1 mmol CaCO₃ uses 2 meq alkalinity and 40.08 mg calcium (20.04 ppm Ca per meq/L)
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