Well personally any plants are good, better to stick with plastic as they are easier to keep care of aswell as they last alot longer!
But i would say real plants look nicer in sand and also move with any water movement, but ive heard that real life plants can attract snails? thats why i dont have them myself.
Maybe a big leaved plastic plant? they look almost like the real life ones and fishies love to swim inbetween them? just a suggestion?
xCowlesy: You just have to make sure that you buy the plants with a guarantee of no snails...That's what I do and I never get any. I think that real plants definately look nicer, especially if you have sand.