The sensor can be cleaned at regular intervals depending on the fouling condition at the site. The cleaning procedure of the sensor spots should be done with caution so that the protective coating is not removed. If the fouling is calcareous it can normally be dissolved with household vinegar. Another substance that can be used is commercially called muriatic acid, which is a 5% HCl solution (dilute solution by 50% should be tested to see how well it dissolves growth before using a stronger concentration).
If needed, the Optode can be submerged in vinegar/HCl over night, or longer. If the marine growth remains use Q-tips to gently wipe it off after it has been softened by soaking in vinegar/HCl. After cleaning the sensor it should be rinsed well in clean tap water before storing or reuse. You can also use methanol and ethanol for the cleaning procedure. Do not use other organic solvents such as acetone, chloroform, toluene since these and others will damage the foil.
The sensor membrane can also be cleaned using a 3% H2O2 solution or rinsing it with ethanol.