Is it obligatory to clean the underground tank after the Shaykh told our neighbors that there was magic in it?

The default rule is that it is permissible to clean the water tank at any time. In fact, it may be necessary from a health perspective due to the accumulation of dirt. It is permissible for a Muslim to perform ruqyah (definition) on themselves or to seek ruqyah from someone whose religiosity is trusted, whether they are afflicted or not. One should not pay attention to the words of the man who claims knowledge of placing magic in the tank, as he may be a liar or deal with devils. Believing him is forbidden and increases imaginary fears. They should fortify themselves with the prescribed morning and evening adhkar (remembrances) and adhere to Islamic injunctions and avoid sins, so that Allah may protect them.