As corals grow, they pull alkalinity and calcium out of the water to build skeletons, along with smaller amounts of magnesium. Water changes replace some of it. In a growing reef, especially one with stony corals, consumption eventually outpaces water changes. A dosing pump solves that by adding small, scheduled amounts of supplement throughout the day, so parameters stay flat instead of sawing up and down.
What you'll need
- A dosing pump with enough heads. Most two-part dosing uses two heads, one for alkalinity and one for calcium. A third head for magnesium or a trace supplement is useful.
- A two-part supplement system. Alkalinity and calcium are sold as a matched pair, often with a separate magnesium product.
- Reliable test kits. Alkalinity is the one you'll test most. Calcium and magnesium get tested less often.
- Containers for each supplement, plus rigid tubing holders to secure lines above the water surface.
- A graduated measuring cylinder for calibration.
Kamoer X1 Pro 2 Dosing Pump
$$Best for: Reefers who want app control and a compact multi-head doser
Kamoer is one of the most common dosing-pump brands in the hobby. The X1 Pro line offers app-based scheduling in a compact housing, which makes splitting doses into many small portions simple.
Why it makes the list
- App-based scheduling
- Compact multi-head design
- Popular with a big user base
Watch out for
- Relies on Wi-Fi and app setup
- Tubing wears over time and needs periodic replacement
Jebao DP-4 Dosing Pump
$Best for: Budget four-head dosing
Jebao's DP-series dosers are budget workhorses with four heads, which covers alkalinity, calcium, magnesium, and one extra. Programming is done on the unit rather than an app.
Why it makes the list
- Four heads at a low price
- No app dependency
- Good for straightforward schedules
Watch out for
- On-unit programming is fiddly
- Build quality is basic, so calibrate often
Hanna Instruments HI772 Alkalinity Checker (dKH)
$$Best for: Anyone dosing alkalinity, which is the parameter you'll test most
Hanna's pocket checkers are common in reef tanks because they give a numeric readout instead of a color-matching guess. The HI772 reads alkalinity in dKH.
Why it makes the list
- Digital readout removes color matching
- Compact and quick
- Widely used by reefers
Watch out for
- Reagents are an ongoing cost
- Cuvettes must be clean for accurate results
Step 1: Measure daily consumption
You can't set a dose until you know how much your tank uses. Alkalinity is the easiest to measure, and it's the most sensitive, so start there.
- Test alkalinity at a set time. For example, 8 p.m. Write it down.
- Don't dose or do water changes for 24 hours. Leave everything else normal.
- Test again at the same time the next day. The difference is your daily consumption. If alk dropped by 1 dKH, your tank consumes about 1 dKH per day.
- Repeat for accuracy. A second measurement cycle smooths out test errors.
- Measure calcium over a longer window. Calcium consumption is harder to read day to day. Many reefers test calcium over several days and dose calcium in proportion to alkalinity.
Step 2: Convert consumption into a dose
Your supplement's label states how much raises a given volume of water by a given amount. For example, it might say a certain number of milliliters raises a certain number of gallons by 1 dKH. Use your total system volume, meaning display plus sump, minus the space taken up by rock and sand. Here's a worked example using stated assumptions rather than a specific product:
| Input | Value (example assumptions) |
|---|---|
| Total system water volume | 100 gallons |
| Measured daily alk consumption | 1 dKH per day |
| Label: dose to raise 100 gal by 1 dKH | X mL (from your product's label) |
| Daily alkalinity dose | X mL per day |
If your product's label uses different units or volumes, scale proportionally. Many two-part systems are designed so the calcium dose roughly matches the alkalinity dose by volume. Follow your specific system's guidance.
Step 3: Calibrate every head
A dosing pump is only accurate if each head is calibrated. Peristaltic tubing wears and changes output over time.
- Prime the lines. Run each head until supplement flows out the end of the line with no air.
- Run the calibration routine into a measuring cylinder. Most pumps dispense for a set time. You then enter the measured volume.
- Repeat for each head. Every head is different, even on the same pump.
- Recalibrate regularly. Monthly is a common routine, and always after replacing tubing.
Step 4: Split doses and separate them
- Split each daily dose into many small portions. Dosing 24 small doses spread across the day keeps parameters flatter than one large dose.
- Don't dose alkalinity and calcium at the same time. Stagger them by at least several minutes.
- Don't dose them in the same spot. Concentrated alkalinity and calcium meeting in one place can precipitate calcium carbonate. That wastes supplement and can cloud water.
- Dose into high-flow areas, such as the sump's return chamber, so supplements disperse quickly.
Step 5: Place the lines safely
- Secure dosing lines above the waterline. A line below the waterline can siphon tank water back into the container, or siphon supplement into the tank.
- Use rigid line holders and check valves where recommended.
- Keep supplement containers lower than the dosing pump where possible, and cover them.
- Label everything. Mixing up alkalinity and calcium lines is an easy mistake with bad results.
Step 6: Test, adjust, and repeat
For the first couple of weeks, test alkalinity daily at the same time. Adjust the dose in small increments until it holds steady. Once stable, many reefers test alkalinity a few times a week and calcium and magnesium weekly. Consumption rises as corals grow, so expect to increase doses gradually over months.
Remember that water changes interact with dosing. If your salt mixes with elevated alkalinity, large changes can bump alk up on top of your dose. Our reef salt guide covers how to match salt to a dosing regimen.
Troubleshooting common dosing problems
| Symptom | Likely cause | Fix |
|---|---|---|
| Alkalinity keeps climbing | Dose too high, or high-alk salt stacking with dosing | Reduce dose in small steps; review salt choice |
| Alkalinity keeps falling | Consumption rising as corals grow | Remeasure consumption and increase slowly |
| White precipitate near dosing point | Alk and Ca dosed together or into low flow | Stagger timing and move lines to high-flow spots |
| Dose volumes drifting | Worn tubing or outdated calibration | Recalibrate; replace pump tubing |
Frequently asked questions
How do I calculate how much alkalinity to dose?
Measure how much alkalinity your tank consumes in 24 hours without dosing, then use your supplement's label to convert that drop into milliliters for your total water volume. Start below the calculated dose and adjust.
Can I dose alkalinity and calcium at the same time?
It's best not to. Stagger them by several minutes and dose them in different high-flow spots to avoid calcium carbonate precipitation.
How often should I calibrate a dosing pump?
Monthly is common, plus whenever you replace the pump tubing. Peristaltic tubing wears and output drifts.
How much can I raise alkalinity per day?
A frequently cited hobby guideline is no more than about 1 dKH per day. Correct low alkalinity gradually.
Do I need a dosing pump for a reef tank?
Not always. Soft-coral and lightly stocked tanks often get enough from water changes. Growing stony-coral reefs usually need dosing to keep alkalinity and calcium stable.