Test alkalinity daily for the first few days when you start or change a dose, then every two or three days until readings are steady for a week or two, then weekly. Test at the same time each day, and test again after any change to corals, feeding or the dose itself.
A schedule by stage
How often you test depends on how confident you are that the dose matches what your tank uses.
| Stage | How often | Why |
|---|---|---|
| Measuring daily use, before dosing | Daily for 3–5 days | To get the consumption figure |
| First week of a new dose | Daily | To catch a dose that’s too high or too low |
| Settling in | Every 2–3 days | Until it’s steady for 1–2 weeks |
| Steady | Weekly | Coral growth slowly changes use |
| After any change | Every 2–3 days for a week | New corals, more feeding, a new product |
Common practice, not a rule. Test more often if your tank uses a lot of alkalinity each day.
Why the same time each day matters
Alkalinity shifts a little between day and night, and dosing pumps add at set times. Testing at 8 am one day and 9 pm the next can make a steady tank look as if it’s moving. Pick a time, ideally before the day’s dosing, and stick to it.
Reading the results
If readings rise day after day, the dose is above what your tank uses; reduce it a little. If they fall, increase it a little. Change the dose in small steps, then give it a few days.
The alkalinity consumption calculator turns a few days of readings into a daily use figure, and can read them straight from your Companion.
When to test more again
Use goes up as corals grow, so a dose that’s right in spring may be low by autumn. A weekly test catches that drift. Go back to every few days whenever you add corals, change the dose, switch products, or see corals looking different.
Common questions
Do I need to test alkalinity every day forever?
No. Daily testing is for setting a dose. Once it’s steady, weekly is usually enough.
What time should I test?
Any time, as long as it’s the same each day. Before the day’s dosing is a good habit.
Should I test calcium as often?
Not usually. Calcium moves more slowly. Every one to two weeks is common.
Sources and limits
Last checked 12 October 2026. Ranges and doses here come from the published sources below and from the chemistry of each additive. They’re starting points for your own tank, not guarantees for any coral.
- Bulk Reef Supply: 10 common water testing mistakes
- Bulk Reef Supply: sodium bicarbonate dosing instructions
- Randy Holmes-Farley, Reefkeeping: Reef Aquarium Water Parameters
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