Disclosure: Coral Compass may earn a commission when you buy through links on this page, at no extra cost to you. Retailer links are marked as sponsored. This doesn't change what we recommend, and we haven't received free products from the brands listed. Full disclosure.
How to choose
Once stony corals start growing, they use calcium and alkalinity faster than water changes can replace them. Two-part dosing, with calcium chloride on one side and sodium bicarbonate or carbonate on the other, is the standard fix. Dose small amounts throughout the day, put the two parts in separate spots or at separate times, and adjust based on alkalinity tests. Use our dosing calculator to work out amounts.
- Calibrate every pump head, then recheck monthly.
- Never let calcium and alkalinity solutions mix in the tubing or the same spot in the tank.
- Raise alkalinity no more than about 1 dKH per day.
For the science behind it, read our Alkalinity, calcium and magnesium guide.
How we review: we paraphrase what owners report in retailer reviews and forum threads, plus picks and test results from BRStv, Reef2Reef discussions and published reef chemists. We only show a rating when we verified it at the source, with the date we checked. We don't invent scores or quotes. Prices and stock change, so check the retailer.
Well-regarded picks
BRS 2 Part Doser (1.1 mL per minute)
Single-head fixed-rate pump
- What reviews say: strengths
- Owners describe it as quiet, simple and very long-lasting, with one reporting 11 years of daily use.
- Weaknesses
- Several reviewers measured real flow well off 1.1 mL/min (for example around 2 mL/min), so you must calibrate. It also needs an external timer or controller.
- Who it's for
- Budget two-part setups and anyone who prefers simple, proven hardware.
- Expert consensus
- BRS names it its "good" tier pick and says it consistently ranks among its top-5 sellers.
Sources
Where to buy:
Neptune Systems DOS QuietDrive
2-head stepper pump (requires Apex)
- What reviews say: strengths
- Owners describe it as very quiet and accurate. Many use it for automatic water changes as well as dosing.
- Weaknesses
- Some report heads failing or not moving water, and it needs an Apex controller plus extra cables for older Apex units.
- Who it's for
- Apex owners who want Trident-driven dosing or automatic water changes.
- Expert consensus
- BRS's "best" tier recommends the DOS for Apex users and heavy jobs like auto water changes. BRS's 2022 list highlights dose adjustments driven by Trident test results.
Sources
Where to buy:
Red Sea ReefDose (2 or 4 head)
App-controlled multi-head doser
- What reviews say: strengths
- App scheduling, notifications, dose logs and reservoir tracking.
- Weaknesses
- It depends on WiFi and the ReefBeat app. We didn't find enough verified owner reviews to summarize.
- Who it's for
- Reefers who want an app-driven doser without an Apex.
- Expert consensus
- BRS's 2022 list calls it one of the most convenient and feature-rich dosers, and its 2026 guide places it in the "better" programmable tier.
Sources
Where to buy:
BRS 2-Part Pharma Calcium and Alkalinity Starter Package
Two-part supplement kit
- What reviews say: strengths
- Buyers say the chemicals work well with BRS's online calculator, and many call it the easiest way to start dosing.
- Weaknesses
- Many reviews criticize the included pump-top bottles for leaking or not sealing.
- Who it's for
- First-time two-part dosers.
- Expert consensus
- Two-part dosing as most reefers do it traces back to chemist Randy Holmes-Farley's published DIY recipe (calcium chloride with baking soda or baked soda ash, plus magnesium). Commercial "Recipe 1" kits follow the same chemistry.
Where to buy:
Spot an error or a product we should add? Specs and availability change often, so always check the manufacturer's current listing.