Gyres are quite almost silent. The only time I hear them is when everything is off and I am trying the listen for them. they did take a week to get that quite but they started just a quiet as my jeabos. I have two large ones in my 6 foot tank. Way too much but, one would blast one side of the tank. I would do two small ones, if I got to do it over again. Big ones are at 30 percent max. They move a lot of water and I love them.