Well, yes, that's normal. And yes you can breed red oscars with tiger oscars. Best way to sex is by venting, do some searching on this bbs, search for like "ovipositor", "genital papillae", "barrel", "oval shaped", "dark spots", etc...in-short, male(narrow tube), female(wider-barrel(oval)shaped) called the "ovipositor".
------------------
Joe
www.cichlidfish.com