I've been keeping angels for 30+ years and can tell you angels do best with Pearl, Dwarf, or Honey Gourami's. And even then there can be problems. Thing is alot depends on the disposition of the angels and the gourami's. Some can be mellow and others not. In a 55g if stocked properly you could do 2 angels and a nice Pearl gourami. But be sure when setting up the tank that there is alot of plants and some very tall ones to break the line of sight up from one end of the tank to the other. Angels mature at 8 months of age so if you get them small, dime to nickle sized bodies, and raise them around small fish they are generally more adapt to leave the small fish alone as the angels mature. On rare ocassion you will get a very aggressive mature large male that can be hard on little fish but this doesn't happen alot. So while I personally wouldn't do neons I do keep both Cardinal and Rummynose with angels very sucessfully. Right now I have 12 breeding angels with 25 Cardinal and 25 Rummynose tetra's in my 220g planted. In a 55 you could do 2 angels, a gourami, 1 or 2 schools of small fish, and cory cats or loaches for the bottom.
