I also have a 25g tank (mine is 24X12X20) and I would reconsider the silver tips if I were you. They're great fish, but very active. I had 9 of them them in my 40b tank and I don't think I'd like to see them in my 25g, even at 24" long.
Maybe consider something like dwarf pencilfish, Beckfordi pencilfish or green neons. I'm not a fan of regular neons, but the green neons are really nice.