my 29g planted tank has kuhli loaches, a couple male guppies, 8 neon tetras and a couple cories(i should have at least 6 but they are left over from what came in the tank when i bought it) in it and they all get along well.... if you just want one fish you could go for an angel fish. it will get nice and big in there. it depends what kind of look you are going for. other good options would be danios, a couple female bettas, some other variety of small tetra, a couple of the smaller species of rainbow fish. don't go for anything that gets big or tends to make a mess...for example most botia type loaches will distroy plants if given the chance, plecos will dig them up and make a mess and some other species like goldfish will just eat them all up.