Dennerle pH Permanent Test

The Dennerle pH Permanent Test is a passive, continuous pH monitoring device that attaches to the inside of the aquarium and changes color in real time according to the current pH level. A small indicator fluid inside the sealed unit reacts to ambient pH, shifting through a spectrum that is matched against the included reference card for readings between pH 5.5 and 8.5. This allows hobbyists to monitor pH changes throughout the day and night without performing individual tests, making it especially useful for CO2-injected planted tanks where pH swings are common. The device requires no electricity, no reagents, and no active maintenance. Replace the unit every 3–4 months for continued accuracy.