Your Dosing Playbook
You have confirmed your tank needs dosing. Your parameters are dropping between water changes, and you understand how calcium, alkalinity, and magnesium work together. Now it is time to act.
This guide is a two-week playbook that takes you from first dose to a dialed-in routine. Follow it day by day. By the end of week two, you will know your tank's consumption rate and have a repeatable schedule that keeps the Big Three locked in.
If you are not sure whether your tank actually needs dosing yet, start with our guide on when to start dosing your reef tank. Come back here when you are ready to begin.
What You'll Need
Gather everything before Day 1. You do not want to pause mid-routine because you are missing a syringe.
Before Day 1: Establish Your Baseline
Test all three parameters on two separate days and record the results. Do not start dosing until you have a reliable baseline. If your magnesium is below 1250 ppm, raise it to 1350 ppm over several days before proceeding — low magnesium makes calcium and alkalinity impossible to stabilize.
| Parameter | Target Range | Your Reading (Day A) | Your Reading (Day B) | Average |
|---|---|---|---|---|
| Alkalinity | 8–9 dKH | ______ | ______ | ______ |
| Calcium | 400–450 ppm | ______ | ______ | ______ |
| Magnesium | 1300–1400 ppm | ______ | ______ | ______ |
Hanna Alkalinity Checker Guide
Get accurate, repeatable alkalinity readings with our step-by-step interactive guide.
Salifert Calcium Test Kit Guide
Follow our step-by-step guide to test calcium accurately before you start dosing.
Salifert Magnesium Test Kit Guide
Verify your magnesium baseline with precise, repeatable readings.
Magnesium Dosing Calculator
Calculate exactly how much magnesium supplement you need to reach your target.
The Week 1 Dosing Diary
This is where the routine begins. Follow each day exactly. Do not skip tests — the data from this week determines your long-term dosing amounts.
Day 1: First Dose
Test alkalinity and calcium. Enter your results and tank volume into the dosing calculators to get your calculated daily dose. Start at 75% of the calculated amount — this gives you a safety margin while you verify your consumption math.
Dose alkalinity (Part A) in the morning. Wait at least 30 minutes, then dose calcium (Part B). Never add both at the same time — they can precipitate out of solution and cloud your water.
Record everything: test results, dose amounts, and the time you dosed.
Alkalinity Dosing Calculator
Enter your current and target alkalinity to get your exact daily dose.
Calcium Dosing Calculator
Calculate the right calcium supplement amount for your tank volume and consumption.
Day 2: Dose Only
Dose the same amounts as Day 1 at the same times. No testing required today — you are letting the first dose take effect and establishing consistency. Measure each dose with the same syringe or graduated cup you used yesterday. Small measurement errors compound over time, so build the habit of precise measurement from the start.
Day 3: Test and Adjust
Test alkalinity and calcium again. Compare to your Day 1 readings.
- Alkalinity dropped more than 0.3 dKH → Your dose is too low. Increase by 10–15%.
- Alkalinity held steady or rose slightly → Your dose is in the right range. Stay the course.
- Alkalinity rose more than 0.5 dKH → Your dose is too high. Reduce by 15–20%.
Apply the same logic to calcium. Recalculate if needed.
Alkalinity Dosing Calculator
Recalculate your alkalinity dose based on your Day 3 readings.
Days 4–6: Hold Steady
Dose your adjusted amounts daily. No testing needed — you are building the habit and letting the routine settle. Keep logging your dose amounts and times. If you notice any cloudiness after dosing, you are likely adding both parts too close together or dosing too fast. Slow down and space them at least 30 minutes apart. Pour each dose into a high-flow area of the tank so it disperses quickly rather than pooling in one spot.
Day 7: Weekly Check
Test all three parameters: alkalinity, calcium, and magnesium. This is your first full-week snapshot.
- Compare to your original baseline. Ideally, all three are within their target ranges.
- If magnesium has dropped below 1300 ppm, add a magnesium supplement dose. Magnesium depletes slowly, so a weekly top-up is usually enough.
- Recalculate your daily dose amounts based on the full week of data.
Alkalinity Dosing Calculator
Use your Week 1 data to refine your daily alkalinity dose.
Calcium Dosing Calculator
Recalculate calcium dosing based on a full week of consumption data.
Week 2: Dialing It In
Days 8–13: Consistent Dosing
You now have a working daily dose from Week 1. Dose the same amounts every day at the same time. Test alkalinity and calcium on Day 10 as a mid-week check.
If your Day 10 readings are within 0.2 dKH (alkalinity) and 10 ppm (calcium) of your targets, your routine is dialed in. Keep going. If readings are drifting, make one small adjustment — no more than 10% up or down — and hold for the remaining days.
Day 14: The Two-Week Review
Test all three parameters one final time. You should now have enough data to answer three questions:
- What is your daily alkalinity consumption? Average the drops you measured across both weeks.
- What is your daily calcium consumption? Same calculation.
- Is magnesium holding steady? If it dropped more than 50 ppm over two weeks, add magnesium to your weekly schedule.
If all three parameters are within target ranges and stable, your routine is set. Move to a weekly testing cadence for alkalinity and calcium, and test magnesium every two weeks.
Alkalinity Dosing Calculator
Finalize your long-term daily dose based on two weeks of real data.
Manual Dosing vs. Dosing Pump
Once your routine is stable, you have a choice: keep dosing by hand or automate with a dosing pump.
Manual Dosing
- Cost: Low — syringes and measuring cups only
- Flexibility: Easy to adjust dose on the fly
- Consistency: Depends on you remembering every day
- Best for: Beginners still learning their consumption rate
- Downside: Missed doses happen — vacations, busy days, forgotten alarms
Dosing Pump
- Cost: Moderate — $80–$300 for a basic peristaltic pump
- Flexibility: Requires reprogramming to adjust
- Consistency: Doses automatically at the exact same time daily
- Best for: Established routines with known daily amounts
- Downside: Pump failure or calibration drift can overdose or underdose silently
Start manual. Once you have two to four weeks of stable results and know your exact daily dose, investing in a dosing pump makes sense. Automate the known — do not automate the guess. Even after switching to a pump, continue testing weekly. Pumps can drift in calibration over months, and catching a 5% dosing error early is far easier than correcting a parameter crash later.
Tracking Your Results
A log is the single best tool for spotting trends before they become problems. Record every test and dose, even when things are stable. Here is a sample format:
| Day | Alk (dKH) | Ca (ppm) | Mg (ppm) | Alk Dose (mL) | Ca Dose (mL) | Notes |
|---|---|---|---|---|---|---|
| 1 | 8.2 | 420 | 1360 | 30 | 28 | First dose at 75% |
| 3 | 8.0 | 415 | — | 30 | 28 | Holding steady |
| 7 | 8.1 | 410 | 1340 | 33 | 31 | Bumped dose 10% |
| 10 | 8.3 | 425 | — | 33 | 31 | On target |
| 14 | 8.2 | 420 | 1330 | 33 | 31 | Routine dialed in |
If you see alkalinity or calcium trending down over three or more entries, increase your dose by 10%. If trending up, decrease by 10%. Small, data-driven adjustments beat large corrections every time.
What's Next
You have a working dosing routine. The next step is fitting it into a broader maintenance system that covers water changes, equipment checks, and parameter tracking on a consistent schedule. Our reef tank maintenance schedule gives you the complete framework.
For a deeper understanding of why these three parameters behave the way they do — and what to do when something goes sideways — revisit the calcium-alkalinity-magnesium relationship explained. The better you understand the chemistry, the faster you can troubleshoot.
Dose consistently. Test regularly. Adjust with data. That is the entire game. Your tank's consumption will change over time as corals grow and new livestock arrives, so revisit your dosing amounts every few months. The system you built in these two weeks — test, adjust, log — is the same system you will use for as long as you keep a reef.