A reef aquarium dosing pump solves one of the most tedious problems in reef keeping: maintaining stable calcium, alkalinity, and magnesium levels as corals actively consume them every hour of every day. Manually testing and dosing supplements once or twice daily works for smaller systems or slower-growing coral collections, but as a reef matures and coral density increases, parameter drift becomes the most common cause of coral stress and loss. An automated dosing pump delivers precise volumes of supplements on a scheduled cycle, often six to twelve times per day, keeping levels far more stable than any manual routine can match.
This guide is specifically about dosing pumps in the context of reef tanks, covering what to dose, how to choose between pump types, recommended models, and the setup process that gets you from "I have no idea what my tank consumes" to a dialed-in automated system.
What Reef Tanks Need to Dose and Why
Stony corals build their skeletons from calcium carbonate. Every unit of coral growth removes calcium and carbonate alkalinity from the water in a roughly 1:1 molar ratio. In a reef tank without replenishment, calcium and alkalinity drop continuously.
The target parameters most reef hobbyists aim for are: - Calcium: 400 to 450 ppm - Alkalinity: 8 to 10 dKH (with SPS, many keep a tighter range like 8.5 to 9.0 dKH) - Magnesium: 1250 to 1350 ppm (magnesium helps calcium and alkalinity stay in solution and consume at a stable ratio)
Water changes with a quality reef salt partially replenish these, but not at the rate a thriving SPS system consumes them. A 100-gallon SPS-heavy tank might consume 50 to 150 ml of two-part supplements daily. Topping that up manually twice a day while trying to dose evenly is unreliable. Spread across 12 automated doses of 10 to 12 ml each, the parameter swing during any given hour becomes almost invisible.
Pump Types for Reef Dosing
Peristaltic Dosing Pumps
Peristaltic pumps dominate the reef hobby because they're accurate, quiet, and low maintenance between tubing replacements. They work by rollers squeezing flexible silicone or Tygon tubing, pushing liquid forward in a consistent stream.
The BRS Dual Dosing Pump is the entry-level workhorse. It's a two-channel peristaltic unit with a simple on/off timer, widely used for basic two-part dosing. Calibration takes about ten minutes, and the tubing is inexpensive to replace. At around $50 to $60, it's the starting point for most new reefers.
The Kamoer FX-STP is a popular upgrade. It's Wi-Fi connected and app-controlled, comes in 2, 3, and 4-channel variants, and delivers doses on a schedule as frequent as every 30 minutes. Accuracy is strong at plus or minus 2%, and the app lets you set different volumes per channel. Retail price runs $100 to $150 for the two-channel version.
The Neptune Systems DOS is the top choice for aquarists running an Apex controller. It integrates directly with the Apex OS, enabling parameter-aware dosing adjustments, consumption logging, and leak detection integration. The DOS retails at $220 to $270 and requires an Apex system to unlock its full feature set. Without Apex, it still works as a standalone dual-channel pump.
Multipart Dosing Systems
For systems that go beyond two-part and need independent channels for magnesium, trace elements, amino acids, or specialized coral supplements, a four-channel pump like the Kamoer X4S or the GroTech TEC Plus 4 handles up to four separate dosing schedules from one unit. These run $150 to $350 depending on brand and features.
For our full analysis of the top models on the market, including how they stack up on accuracy, compatibility, and value, see our Best Dosing Pump for Reef Tank guide.
Establishing Consumption Before You Dose
The most common mistake new reef dosers make is programming a pump before they know their tank's actual consumption rate. If you set the pump based on a general guideline without measuring your specific tank, you'll either overdose (causing parameter spikes) or underdose (leaving parameters to drift down anyway).
Here's the process:
- Test alkalinity at the same time each morning for five consecutive days without any supplementation. Note the daily change.
- Calculate the ml of your chosen supplement needed to replace that daily loss. For BRS two-part, approximately 1.25 ml per gallon raises alkalinity 1 dKH. So if a 60-gallon tank drops 0.5 dKH daily, you need about 37.5 ml of Part B daily to hold steady.
- Measure calcium over the same period and set Part A volume to roughly match Part B, then adjust based on test results.
- Divide the daily volume into equal doses scheduled across the day. For 37.5 ml daily in 12 doses, each dose is approximately 3 ml.
- Monitor weekly for the first month and adjust volume as coral growth increases or seasonal changes alter consumption.
Placement and Plumbing Tips
Where the dosing lines deliver supplement matters more than most hobbyists realize.
Dose into high-flow areas. Never dose directly onto coral tissue. Calcium and alkalinity supplements are highly alkaline or acidic before they dilute into tank water. Delivering them into the return pump output or sump return section where high-flow turbulence immediately dilutes them prevents local pH spikes near corals.
Keep intake tubes submerged in the solution container. If the intake tube draws air, the pump skips doses without any indication. Weight the intake end with a small metal nut or buy intake weights designed for this purpose.
Label each channel clearly. Mixing up Part A and Part B in the wrong container is a surprisingly common mistake that can cause calcium and alkalinity to crash simultaneously. Use different colored tubing for each channel if your pump supports it.
Run lines at the lowest reasonable height. Peristaltic pump tubing develops micro-kinks if routed with sharp bends. Gentle curves and a clean line run reduce tubing wear and improve dose consistency.
Alternatives to Two-Part Dosing Pumps
Two-part isn't the only approach, and for some reef systems other methods make more sense:
Calcium reactor: Dissolves calcium carbonate media in CO2-acidified water, releasing calcium and alkalinity into the tank continuously. More expensive upfront ($200 to $600 for reactor, regulator, and media), but the per-gallon cost of calcium and alkalinity replenishment drops significantly at scale. Calcium reactors work best in large SPS systems where two-part costs $50 to $100 monthly.
Kalkwasser reactor: Mixes saturated lime (calcium hydroxide) and delivers it via the evaporation top-off line. Raises both calcium and alkalinity simultaneously while also maintaining elevated pH. Less precise than two-part dosing but very effective in systems with modest demand and moderate evaporation rates.
Balling method: A more precise variant of two-part that accounts for natural ionic balance shifts in reef tanks. Uses three separate solutions (calcium chloride, sodium bicarbonate, and magnesium chloride/sulfate) in carefully calculated ratios. Often paired with an automatic water change system.
See our Best Aquarium Dosing Pump guide for more on how dosing fits into a broader reef system strategy.
FAQ
How often should a reef dosing pump deliver supplements? More frequent, smaller doses produce more stable parameters than fewer large doses. Dosing six to twelve times daily is the standard approach. Some advanced reefers with fast-growing SPS dose every hour. The practical floor is three times daily; less than that and you'll see noticeable intraday swings in alkalinity, which SPS corals respond to negatively.
Do I need to dose magnesium separately? It depends on your salt mix and consumption rate. In many reef tanks, regular water changes maintain adequate magnesium without supplementation. If you're testing below 1250 ppm, either increase water change frequency, switch to a higher-magnesium salt, or add a dedicated magnesium dosing channel. Magnesium consumption is much slower than calcium and alkalinity in most systems.
Can I use a dosing pump for other additives besides two-part? Yes. Dosing pumps are also used for coral amino acids (like Red Sea Reef Energy B), trace elements (Aquaforest Probiotic Reef Salt component supplements), and even food dosing (phytoplankton for filter feeders). Each additive gets its own channel and calibrated schedule.
What happens if my dosing pump misfires or overdoses? An overdose of alkalinity is the most dangerous failure mode. Rapidly elevated alkalinity causes "alkalinity burn," where coral tissue turns white from the outside in, starting at the tips in SPS. If you suspect an overdose, stop dosing, run large water changes to bring alkalinity back toward target, and identify the cause (usually tubing failure or calibration error) before resuming. This is why testing weekly is important even with an automated system.
Final Thought
An automated dosing pump isn't optional for a serious SPS reef. Once your tank reaches a coral density where parameter stability directly determines coral health, manual dosing once or twice a day introduces enough variability to cause ongoing low-level stress. Set up the pump properly with measured consumption data, dose in small frequent increments, and verify parameters weekly for the first month. After that, the system largely runs itself and your corals will show it in their growth and color.