From what I saw it seemed like you could just leave the PH sensor in the tank for long periods of time with out attention.
Also, this is not for fish. It's for algae.
How long do you think that will last?
Also do I just leave the sensor in the tank or do I need to extract a sample from the water and place it into the sensor.
Also, this is not for fish. It's for algae. http://www.algaelab.org