The Aeration Test
To run the test, you’ll need an 8 oz cup of tank water, a calibrated pH probe, a timer, an air pump with an air stone, and access to the outdoors. Only use a small cup because off-gassing carbon dioxide is very time-consuming. A small sample ensures the water will be fully equilibrated after the set time for accurate results.
- Measure the aquarium’s initial pH.
- Take a cup of tank water and heavily aerate it indoors for an hour. Record the pH.
- Take the cup and repeat the same process outdoors for an hour. Record the pH.
*Keep in mind that temperature differences can affect pH readings. Ensure both samples are near the same temperature when recording the pH. The diagnostic results are here:
1) If heavily aerating a cup indoors increases the pH, there is either not enough aeration or some filtration/maintenance routine is adding too much CO₂ or H⁺.
2) If aerating the cup indoors doesn’t meaningfully raise the pH, but aerating it outdoors does, the culprit is excess indoor carbon dioxide entering the tank. The solution is to increase the pH-boosting methods ('Managing pH in Reef Tanks: Part Two' will discuss how).
3) If both the indoor and outdoor cup pH values remain low after the test, or if the outdoor sample rises, but not meaningfully, then the probe, test kit, calibration, or buffer standards are very likely inaccurate. The outdoor aeration part of the test determines if the probe is accurately responding to low CO₂ conditions and shows how concentrated the indoor CO₂ is.
