When the water has been purified, it is stripped of chemicals that would normally prevent the growth of algae. This is one factor that can allow algae to potentially occur. The second is light. If the Berkey is near a window and in the sunlight, the combination of the purified water and heat from the sun provides ideal conditions for algae to grow. The LED Light of the Berkey Light Stand can create the same effect if left on too long.
The growth of algae can be avoided by relocating the system away from direct sunlight or by not using the LED lights as frequently. It is also important to wash the plastic housing monthly with soap and water. Our customers have reported that by placing a pure silver coin in the lower chamber, that the algae is unable to grow. This is due to the natural anti-microbial properties of silver. If you prefer this option, an American Eagle coin (99.999% pure silver) would work well. While we would not know the exact type of algae that is growing, most blue-green algae’s are healthful food sources. We suggest Googling spirulina for more information about blue-green algae being healthful.