Emergency playbook
Overdosed alkalinity, calcium or another additive: what to do
The danger is speed: a big, fast change in alkalinity or pH stresses corals more than a high reading held steady.
Do this now
- Unplug the doser, or stop adding the product.
- Test alkalinity, calcium, magnesium and pH. If you suspect kalkwasser, test pH first.
- Check the test: run it twice, and check the kit is in date.
- If pH is very high after kalkwasser or the water is turning white, do a water change with tested, matched salt water.
- If an unknown chemical went in, add fresh activated carbon and do a water change.
Why each step
- 1. Unplug the doser, or stop adding the product.
- Most overdoses come from a pump stuck on, a doubled dose, or a mix-up between bottles (Reef Builders on doser failure).
- 2. Test alkalinity, calcium, magnesium and pH. If you suspect kalkwasser, test pH first.
- You need to know which one is high before you act. BRS warns kalkwasser should never raise pH by more than 0.2.
- 3. Check the test: run it twice, and check the kit is in date.
- A wrong reading leads to a wrong correction.
- 4. If pH is very high after kalkwasser or the water is turning white, do a water change with tested, matched salt water.
- A pH spike and the precipitation that follows harm corals quickly. A water change brings both back towards normal.
- 5. If an unknown chemical went in, add fresh activated carbon and do a water change.
- Our reading: carbon removes many organic chemicals, and a water change dilutes the rest.
Once the tank is stable, what next?
- For alkalinity or calcium that is high but steady: pause dosing and let the tank use it up. Red Sea advises pausing and resuming at a corrected dose once the level falls back.
- Test daily at the same time while it falls.
- Restart dosing at the corrected amount, spread across the day.
- Check salinity: a large dose of liquid can change it slightly.
How do I stop it happening again?
- Keep the doser bottle small: no bigger than a few days of dosing, so a stuck pump cannot empty a month of supplement into the tank (our reading).
- Calibrate the doser monthly and replace worn tubing (Reef Builders).
- Never put kalkwasser in an ATO reservoir without knowing the most it could add in a day.
- Label every bottle and every doser head.
Where do sources disagree?
| Topic | What sources say | Our reading |
|---|---|---|
| How fast to bring a high reading down |
| If it is high but steady and the corals look normal, pausing is gentler. If corals are reacting or pH is spiking, a water change is safer. |
Last checked . How we check