Review on Pawfly 4 Inch Air Stone Disc Bubble Diffuser: Enhance Your Aquarium with Suction Cups! by Gloria Shaw

I just bought four of these air stones and added two of them to my 75 gallon tank. Before using, these air stones were immersed in water for 12 hours. I have two air pumps and for one of the pumps, two of the four didn't work properly, but my second "Tetra" air pump had no problems so make sure it's not your air pump. I have two running around my aquarium and they look great. I would recommend these air stones, make sure you soak them in water for at least four hours and make sure your pump is compatible with them.