I'd cap one uplift tube, buy a new gang valve and run the single tube with a
minimal air stream. Just enough to pull enough fresh water into the UGF to
prevent anaerobic conditions.

"Scott Rogahn" wrote in message
...
I turned the air pump back on. The gang value to the airstones does not
adjust well, they are either on or off. so I can't slow the air bubbles.
Would a power head agitate the surface less than the air stone. If so
would
I need a power head for each riser? If I use one power head what stops
water from being draw down the other riser rather than through the gravel?