What pH probe do I have?

There are several types of pH probes available, the most common that you will have had provided with your unit/controller is a Gel filled with Double Junction pH probe.

How should it be used?

The lifespan of pH electrodes is a question that no one can definitively answer. It depends upon so many variables, but for aquarium use many of these can be eliminated.

• Ideally the probe should be kept in the dark to prevent the growth of algae on the delicate glass membrane, as this blocks the pores.
• The probe must be kept in a clean part of the tank – away from silt and sediment.
• Always keep the tip of the probe wet, to prevent it drying out.
• Never get the cable wet – leaving the probe cable in water will cause it to swell and slightly absorb some water. This will cause problems with accurate calibration, and could lead to erroneous readings.
• Calibration, cleaning and de-hydration should carried out on a regular basis – best monthly (see below)

How do I clean/maintain the Probe?

Cleaning can be done by immersing the probe in cleaning solution for a couple of hours.

Due to the aquarium water being lower in salt level than the probe contents, the probe will “leach” or absorb water, leaving it less reactive. This leads to “drifting” or slow reaction time. To reverse this, immerse the probe in storage solution for 24 hours. Do not use distilled water to store it.

Providing the probe is still in good condition, calibration should not have to be done often. If the calibration is out every time you check it, then the probe is on the way out. There is no need to calibrate to anything other than 7.0pH – using 4.0pH or 9.0pH to adjust the slope is unnecessary as we are normally dealing in a pH range of 6.0-7.5 in our aquariums, but this will sometimes be affected by the brand of pH controller you have.

Never place the probe in the bottle of calibration solution – this will affect the quality/accuracy of the solution, resulting in a change of the pH value. It is best to pour a small amount of it into a small container and dispose of it after use.

What if the readings still do not seem right?

Another problem that occurs with pH probes is when you get correct readings when the probe is placed in a buffer solution, but incorrect readings when in the tank. This is when the tank water has a ground connection somewhere (and the controller has a ground connection). This may be through a pump, heater, a steel framed tank, or any other connection that may inadvertently cause grounding of the water body. An easy way to test for this condition is to take a glass of aquarium water and place the probe in it to see if the reading is different.

Another problem is when extension cables are used, and the BNC connecter joining the two cables is touching something that can ground it – try wrapping the connectors in insulation tape.

Any other problems with the controller/unit or other items in you CO2/pH products, please contact AQUOTIX for fast and effective advice. We also do repair work on many brands. If there are any further questions regarding Carbon Dioxide and pH in the aquarium or any topic, then please contact a staff member at AQUOTIX. We’re here to help all aquarists.