Two-part dosing adds balanced calcium and alkalinity (and usually magnesium) so consumption doesn't outrun water changes. It's the most popular maintenance method for mixed and SPS reefs.
How Recipe 1 works (simplified)
Randy Holmes-Farley's Recipe 1 alkalinity liquid raises alk by about 1.4 dKH per mL per US gallon; the calcium liquid raises Ca by about 10 ppm per mL per US gallon. Equal daily volumes keep the ratio near natural. Commercial kits (BRS Pharma, Red Sea Foundation, Fritz RPM) follow the same idea with different strengths — always use the label's numbers.
Finding your daily dose
- Get alk stable near your target with manual corrections (raise alk guide).
- Stop dosing for 24 hours and measure how much alk drops. That drop is your daily consumption.
- Convert consumption to mL using your product's strength (or the calculator).
- Dose that volume daily, split into many small doses.
- Recheck alk after 3–4 days and adjust by ~10%.
Dos and don'ts
- Dose alk and calcium into high flow, hours apart.
- Never combine the two parts in one container — they precipitate.
- Keep Mg topped up (magnesium).
- Use reef-grade chemicals, not kitchen baking soda.
Hardware: dosing pumps and 2-part gear guide.
Sources
FAQ
Can I dose by hand? Yes for small tanks; a pump is more consistent.
What if calcium rises but alk falls? Demand may be unbalanced (sulfur denitrator, kalk, reactor). Adjust each side independently.