Just like you, I have a 29 gallon tank and a psuedochromis, though mine is a bicolor. You're right; you don't want to add a royal gramma, and probably not any blennines or gobbies. I also have a tomato clown, a false perc clown, and a green reef chromis. The psuedo gets along with them just fine. I've also had four-stripe and yellow-tail damsels with psuedos before. Really, the psuedochromis will got along with pretty much anything as long as it's not too similar to him. If the psuedochromis suspects that the similar fish is going to be competition, then he'll get aggressive.