I have 2 guppy tanks. One has a little gravel and the other is bare bottom. They seem to like the bare bottom, and it sure makes it easier to get the fry and vac it, but I prefer the looks of the gravel. 
With guppies, it is not uncommon for the fry to get caught in the gravel, so I use a fine gravel as opposed to a larger piece gravel. Also, you can place a few pebbles on the bottom as deco, but I like the sound of the spray painted bottom. Never thought of that...now if I can figure how to paint it while it is set up.
With guppies, it is not uncommon for the fry to get caught in the gravel, so I use a fine gravel as opposed to a larger piece gravel. Also, you can place a few pebbles on the bottom as deco, but I like the sound of the spray painted bottom. Never thought of that...now if I can figure how to paint it while it is set up.