Step-by-step how-to
How to dose 2-part calcium and alkalinity in a reef tank
Step-by-step 2-part dosing protocol. B-Ionic, ESV, Bionic, Tropic Marin Carbo. Calculate the dose, split daily, monitor parameter response.
Intermediate7 steps10 min
Step-by-step
Step 1: Test current parametersTest alkalinity, calcium, and magnesium. Record. Targets: alk 8-9 dKH, calcium 420-450 ppm, magnesium 1300-1400 ppm.
Step 2: Calculate the daily doseUse the Fast Aquatics reef dosing calculator at /calc/reef-dosing/ - enter tank volume + current Ca + alk + Mg. The calculator outputs exact mL of part 1 + part 2 for the day.
Step 3: Verify magnesium firstIf Mg is below 1300 ppm, dose Mg supplement first (Magnesium Pro or
Salifert Magnesium). Calcium and alkalinity will not stabilize until Mg is in range.
Step 4: Set up the dosing pumpRun part 1 (Ca) and part 2 (Alk) through SEPARATE dosing pumps - they precipitate if mixed in the same line. Schedule 8-12 small doses across 24 hours, NEVER one large dose.
Step 5: Test alkalinity after 24 hoursIf alk dropped, you under-dosed. If alk rose above target, you over-dosed. Adjust the daily dose by 10% increments and retest in 48 hours. Never make corrections >0.5 dKH per day.
Step 6: Monitor calcium weeklyCalcium consumption tracks alkalinity. If alk holds but calcium drops, increase part 1 only. If calcium holds but alk drops, increase part 2 only.
Step 7: Recheck Mg monthlyMagnesium should hold steady at 1300-1400. Slow drift is normal; correct gradually with Mg supplement.
Frequently asked questions
What is 2-part dosing?
2-part dosing uses two separate liquids (calcium chloride + sodium bicarbonate-based) to replenish coral consumption. Part 1 + part 2 must be dosed in equal volumes to keep the ionic balance stable.
How much 2-part should I dose?
Depends on coral consumption. Typical: 1-3% of tank volume per day in each part. Use the calculator at /calc/reef-dosing/ for exact amounts.
Can I dose 2-part by hand?
Yes, with a graduated syringe split into multiple doses across the day. Dosing pumps automate this and produce more stable parameters.