You mean to the bulkheads underneath the tank? You can use either regular PVC or vinyl tubing. I would go with at least a small piece of vinyl tubing to ease vibration noise and not make it so permanent.
You can to the inside of the bulkhead but not outside. The bulkhead would work like a coupling fitting does, but I wouldn't recommend it. Nothing fit screw onto the outside of the bulkhead though.
Hello chase. You shouldn't attach vinyl tubing to the outside of the bulkhead. You need to put a barb inside the bulkhead and then attach the vinyl tubing to that like in the pictures I showed you.
