You mean an air-stone? As I understand it; air-stones don't really add air to the water directly - the contact time of the air bubble to the water is too short. What they do is cause surface agitation as the numerous bubbles pop at the surface, which causes the majority of the gas exchange. As you already have good surface agitation, I don't really think that a bubbler would add much value - and it would cause salt to spray all over the place, which would not only make a mess, but also make it harder for you to keep your salinity stable. Air-stones are great for "drop in" temporary aeration (such as when holding a fish in a temporary bucket), but I tend not to see them as a lot of value in a tank that has a full setup of equipment in them.
I agree. You've increased aeration and added some Prime. That combination is a solid effort to bring down your ammonia levels (if, indeed, they are elevated). The only other action I would take myself at this point would be to pick up one of those badges to get a true reeding of your ammonia level. Give it a few hours and if you're really itching to do something, run another test for ammonia. It may say the same thing; it should say less. If it doesn't, it's nothing to panic over - just wait some more and test again in a few more hours. Watch the fish and look for changes in their behavior.
