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Saltwater Aquarium Guide Reef-keeping magazine
Water Chemistry

Calcium Reactor vs Two-Part Dosing: Which Is Right for Your Reef?

A full comparison of the two main reef dosing methods by cost, complexity, parameter stability, and tank size.

By Saltwater Aquarium Guide Published

Dome-shaped stony corals on a sand bed in a reef aquarium
Photo: David Clode / Unsplash
In this article
  1. Two-part automation
  2. Calcium reactor
  3. Verdict

Once your reef consumes more than 1 dKH per day, manual dosing becomes impractical. Both calcium reactors and two-part automation solve the problem differently.

Two-part automation

Three peristaltic pumps dosing alk, calcium, and (sometimes) magnesium. ~$300 for the dosers, $20/month in solution.

Calcium reactor

CO2 lowers pH inside a reactor chamber, dissolving aragonite media. ~$600 setup, $40/year in media + CO2.

Verdict

Two-part for tanks under 90g; calcium reactor for SPS-dominant tanks above 120g.

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