I would not put more than 2 fish in a 12 if one is going to be a royal gramma. They can get pretty big for that size tank. 3-4 is way overstocked. Royal grammas can be quite aggressive with conspecifics{same body shape}. No angel should be kept in a 12 gal. tank. Get a small goby to go with it like an eviota species, clown goby, red banded, green banded, bumblebee goby, neon goby,yasha white ray. Something that stays under 2".