Review on Pawfly Release Airstones Aquarium Hydroponics by Sarah Felder

While not noisy themselves, they are not of very good quality. On arrival 3 of them were working but one was barely leaking air. I followed the instructions and soaked them in water before use. I changed the line thinking it might be the problem and it never got fixed. I am using a 10w air pump with 2x125GPH outputs. In my 50 gallon aquarium I have found that using 4 2" vents provides a lot more air than 3 of these 4" vents. It's like one of the 2 inches blew off one of those 4 inches. They also don't sit well on the underside.