Hey Blinky,I've had guppies and neons together and they have done fine. The thing about neons,is that they are schooling fish and prefer to be in groups. One other tip I'd like to pass along-Alot of people when they start out with tropicals want live-bearing fish,which is great if you know what you're getting into. I started that way myself-bought a couple pairs of guppies and within a couple of months had a gazillion or so! That brings up overstocking,where to put them all,and worse,-the beginning of all kinds of problems if your not careful. The only time I ever had problems with any of my tropical fish tanks,was when I had pairs of live breeders.As long as you think of these issues first off,then you know what your'e in for.It's so easy to go from great to your tank crashing with problems. Good luck with the tropicals! They can be very beautiful tanks! I love mine!