Yes, a valve for each diffuser and located at the edge of where the airline goes into the pond. After adding the third diffuser, I definitely had to balance to the air flow. The TGG pond is shallow, had a 1 inch line and the other two diffusers were in deep water with 3/4 inch lines feeding them. When I first turned on the air to the TGG pond it was like a fountain. Throttled it way back to less than 1/4 open on the valve and it still creates a commotion.