"This is a simple little kit that works surprisingly well. It saves all the mess of the bio kits and lasts longer. I have found that one bottle lasts about 3 months and that is filling the diffuser that sits in the water once a day while the lights are on. The plants certainly appreciate it with full lush growth and a significant decrease in algae. For the smaller tank (around 40-80 cm) this is a great low cost kit to add to ones tank. Highly recommended. "