hey i still post ive just been out of the country, 55 gallon is fine for peacocks but i would not do all peacocks, mix in some haplochromis, Protomelas Steveni (Taiwan Reef), Protomelas taeniolatus (Red Empress), any from the genus Copadichromis, Aristochromis/Otopharynx lithobates, Placidochromis electra, Sciaenochromis fryeri (electric blue ahli), would all be good options for a 55 gallon, id get 8-10 with about half being peacocks and half being haps, also victorian can be mixed like astatotilapia latifasciata/Zebra Obliquedins, Haplochromis sp.44/Red Tailed/Obliquedins/Thick Skin, if you are wondering what on earth these fish are goto
www.cichlid-forum.com which has great articles, a great photo gallery and very helpful members
o btw, tank should have rockwork but does not neat to have tons of it and should have an open sand bed, heres mine as an example,
http://www.freewebs.com/cichlidiot/images/55galfull.jpg , you can also check out the tanks section at cichlid forum, and i would advise against frontosa unless you have a large enough tank like mike posted above