CALCULATOR · DOSING
Reef 2-part dosing calculator (Alk / Ca / Mg)
The short answer
Two-part dosing replaces the alkalinity a reef consumes each day. Once consumption passes ~0.45 dKH/day, water changes can’t keep up. Replacing 1.0 dKH/day in a 50-gallon system takes about 24 mL of ESV B-Ionic or 36 mL of BRS/DIY soda ash daily. This is alkalinity chemistry only.
The ReefRig Dosing Method
Once alkalinity consumption passes ~0.45 dKH/day, water changes stop keeping up. Daily mL = your dKH/day × water gallons ÷ the product’s dKH-per-mL-per-gallon.
Replacing 1.0 dKH/day in a 50-gallon reef takes ~24 mL of ESV B-Ionic or ~36 mL of BRS/DIY soda ash per day.
Daily 2-part dose by water volume
Milliliters per day to replace a reference 1.0 dKH/day of alkalinity consumption. Your tank’s real number scales linearly — measure the 24-hour drop and multiply. Dosing becomes necessary once consumption passes ~0.45 dKH/day.
| Water volume | ESV B-Ionic (Alk) | BRS 2-Part / DIY soda ash |
|---|---|---|
| 10 gal | 4.8 mL | 7.1 mL |
| 20 gal | 9.7 mL | 14.3 mL |
| 30 gal | 14.5 mL | 21.4 mL |
| 50 gal | 24.2 mL | 35.7 mL |
| 75 gal | 36.2 mL | 53.6 mL |
| 100 gal | 48.3 mL | 71.4 mL |
| 150 gal | 72.5 mL | 107.1 mL |
| 200 gal | 96.6 mL | 142.9 mL |
| 300 gal | 144.9 mL | 214.3 mL |
2-part strength reference
| Product | dKH per mL / gal | Notes |
|---|---|---|
| ESV B-Ionic (Alk) | 2.07 | Premixed liquid 2-part; 1 mL/gal raises 0.74 meq/L (2.07 dKH) per ESV. |
| BRS 2-Part / DIY soda ash | 1.4 | BRS 1.5-cups-soda-ash-per-gallon recipe; ~1.40 dKH per mL/gal from BRS calculator example. |
Strengths from manufacturer instructions (ESV) and the BRS soda ash recipe/calculator. 1 meq/L = 2.8 dKH. This tool sizes an alkalinity supplement dose — it makes no health or treatment claims.
LIVE CALCULATOR
Size your daily dose
Enter your water volume and measured daily alkalinity drop (dKH/day), then pick a 2-part. The dose scales linearly — double the consumption, double the mL.
At this consumption, water changes alone stop holding alkalinity steady — a metered daily 2-part dose keeps it stable. Split the dose over the day and re-test after any change. Dose to a measured dKH; this is chemistry, not a health recommendation.