Sorry to tell you this but I think I see red bugs in the first picture.
^---The little orange dots/specs are red bugs on his first photo. They may look like polyps to the untrained eyes but those are red bugs.
What should it be dipped in?
Do these only affect acros?
You dont have enough Red Bugs to warrant treating with interceptor im my opinion.
I had them awhile back what I did is inspect my Acro's daily and if there were any on them I used a turkey baster and blasted them off it takes them awhile to come back with SPS no matter how much you dip or how carefull you are your always going to end up getting red bugs in my opinion.
Nice Acro's by the way good start.