How to prevent air conditioner pipe from molding?

The obvious way would the to thermally insulate the pipe. In this way, the warm air in the room does not come in contact with the cold pipe.

I do not know if you could / should do this by yourself, for safety reasons. Please contact a specialized air-conditioning service for advice.

If the unit is still under guarantee, call the service to fix it for you for free.

Besides the problem with the mod, there is also an efficiency problem - ultimately, a money problem, your money lost in inefficient cooling.