General Hydroponics pH Test Kit 1 oz. (Pack of 24)The General Hydroponics pH Test Indicator can help you maintain an ideal pH level (which is between 5. 5 and 6. 5). This can be achieved by monitoring your pH using the super concentrated drops found with the test indicator. Based on the test results, pH Up or pH down (available separately) can be added to adjust the pH as needed. The General Hydroponics pH Test Indicator works across a wide pH spectrum (pH 4. 0 8. 5). Kit includes sampling tube,