Exactly as others have mentioned. Ive got my 20 Gallon and my 46 gallon tanks on the same Co2 set up.
Single solenoid that connects to a manifold and 2 output needle valves. If you had more then just the 2 you wanted to do you could even do more. Just have to add to the manifold and more needle valves.
Sun Sun pimp #72
RAOK CLUB # 68