Bio ball is utilized to hold the beneficial bacteria from your tank. We advise using it after the water has passed through the filter foam since the foam will remove any debris from the water and capture it, preventing it from getting caught in the grooves of our offering. It is added to skimmer boxes, waterfall filters, or your pond itself to enhance the surface area available for helpful bacteria. The good bacteria will begin to colonize this bio ball as soon as you place it in your tank. You'll have a strong population growth on it after three or four days.