Advanced Calculator Inputs
Example Data Table
| Tank Type | Gross Volume | Displacement | Current dKH | Target dKH | Supplement | Schedule |
|---|---|---|---|---|---|---|
| Mixed reef | 75 gal | 12% | 7.4 | 8.5 | Sodium bicarbonate dry | 3 days, 4 doses daily |
| SPS reef | 120 gal | 15% | 7.8 | 8.3 | Liquid alkalinity supplement | 2 days, 12 doses daily |
| Nano reef | 25 gal | 10% | 8.1 | 8.6 | Sodium carbonate dry | 2 days, 2 doses daily |
Formula Used
Unit conversion: 1 meq/L = 2.8 dKH and 1 dKH = 17.848 ppm as CaCO3.
Net water volume: Net liters = Gross liters × (1 − displacement %).
Water change blend: Starting dKH = Current dKH × old water fraction + New salt dKH × new water fraction.
Required increase: Delta dKH = Target dKH − Starting dKH.
Total alkalinity: Total meq = (Delta dKH ÷ 2.8) × Net liters.
Dry supplement dose: Grams = Total meq × equivalent weight ÷ 1000 ÷ purity fraction.
Liquid dose: mL = Delta dKH × (Net liters ÷ 100) ÷ product strength.
How to Use This Calculator
- Enter the real system volume, including sump water.
- Estimate rock, sand, and equipment displacement.
- Add current alkalinity and target alkalinity.
- Enter a water change plan when one is expected.
- Choose your alkalinity additive.
- Enter product strength for liquid or custom dry mixes.
- Choose a safe daily rise and dosing schedule.
- Submit the form and review the safety notes.
- Download CSV or PDF results for your reef log.
Reef Tank Alkalinity Guide
Why Alkalinity Control Matters
Alkalinity is the buffering capacity that protects reef pH. It also supplies carbonate for coral skeleton growth. Most reef keepers track it in dKH, because the scale is easy to read. A stable range supports calcification. A fast swing can stress corals, clams, and coralline algae.
Testing Before Dosing
Test at the same time each day. Use a clean vial and fresh reagent. Record the value before adding any supplement. Do not chase one strange reading. Retest when the result seems far from normal. Salinity changes can also shift concentration. Water changes can move alkalinity toward the new salt mix level.
Choosing a Supplement
Sodium bicarbonate is gentle and useful for careful corrections. Sodium carbonate is stronger in pH effect and should be split. Sodium hydroxide is very caustic and needs extra care. Liquid two part is simple for dosing pumps. Custom mixes can work well when their strength is known.
Planning Safe Corrections
This calculator converts the chosen unit into dKH first. It estimates the real water volume after rock and sand displacement. Then it calculates the difference between current and target alkalinity. If a water change is entered, the tool blends the old and new alkalinity first. The dose is divided across planned days and daily portions.
Maintenance Dosing
Correction dosing fixes today’s gap. Maintenance dosing replaces daily consumption. Measure alkalinity for several days without changing the dose. The drop per day becomes the consumption rate. Add that value to the maintenance field. Then adjust slowly as coral growth changes.
Interpreting Results
The total dose is the full correction amount. The daily dose spreads that correction across the selected schedule. The per dose value helps with manual dosing or dosing pumps. The maintenance estimate is separate. It is based on daily consumption. Confirm every change with new tests before increasing the program. For safer reef keeping.
Good Reef Practice
Dose into strong flow. Keep additives away from pumps, heaters, and animal tissue. Never mix concentrated alkalinity and calcium solutions together. Use separate containers and lines. Watch pH when using high pH products. Stop dosing when animals look stressed. Stability beats a perfect target number.
FAQs
What is reef tank alkalinity?
Alkalinity measures the water’s ability to buffer acids. It also shows available carbonate and bicarbonate used by corals for skeleton growth.
What alkalinity range is common for reef tanks?
Many reef aquariums run near 7 to 11 dKH. The exact target should match your salt, nutrients, coral type, and dosing style.
How fast should alkalinity be raised?
A cautious correction is often around 0.5 dKH per day. Sensitive systems may need slower changes and more testing.
Can this calculator lower alkalinity?
No. Alkalinity additives raise alkalinity. To lower it, stop dosing, allow normal consumption, or use water changes with lower alkalinity water.
Why does displacement matter?
Rock, sand, and equipment reduce actual water volume. A lower real volume needs less supplement than the tank’s display size suggests.
Which supplement should I choose?
Sodium bicarbonate is gentle. Sodium carbonate raises pH more. Liquid products are convenient. Custom mixes need accurate known strength.
What is daily alkalinity consumption?
It is the alkalinity drop over one day before dosing. Track several days, average the decline, and use that value for maintenance dosing.
Should I trust one unusual test result?
No. Retest before making a large correction. Dirty vials, old reagent, air bubbles, and salinity changes can affect readings.