I have a 5 gallon tank also. You can take a rubber band and twist it around the tubing just enough that will give you the current you feel comfortable with.
5 gallon tank that came with complete set-up. Have to mollys in the tank. It seems right around the front of the tank is where the fish are just fighting against the current. I have two fake plants and two huts they can go in. I don't know, I am new to fish tanks and the current just looks way to rough for them to survive!