Generally, no. The bulbs we use discourage algae and barnacle growth on the bulbs. Silt may settle on the bulb, this can be cleared usually by moving the bulb around a bit. Our bulbs are designed to run each night, so if you plan to leave them off for a period of time, we recommend pulling the bulbs out of the water so they wont grow barnacles. Be aware that the bulbs should not be turned on out of the water.