Not sure what your asking? A "gate" as in gate valve? A solenoid is a motor that could be used to move a valve.
If you are asking whether you need a valve of some kind with an aerator pump ballast setup, the answer is, no, you dont.
If you use a thru-hull mushroom, instead of a scoop, it will not force-fill your sacs, and therefore, no need for a valve.