Clarify your water naturally and cultivate beneficial bacteria with these Polypropylene Bio-balls! They promote gas exchange and increase dissolved oxygen levels, then filter the water as the bio-balls combine with organic waste to dissolve it. Bio balls with their immense surface area per square inch serve as great hosts to beneficial bacteria in aquatic biological filtration systems. In trickle systems the bio balls promote gas exchange and increases oxygen levels. They are really simple to use: place into a mesh bag and drop into the pond filter. Do not clean the bio balls once they are cycled, or you will risk killing off all the beneficial bacteria that you need to filter your water.