If you do not want to breed too many fish, I would suggest that you have just male guppies, otherwise you will end up with a severe case of MTS in no time in order to save the fry.
Usually you have a higher ratio of females to male guppies so that they do not get harassed incessantly by the male, I would consider three females to one male a good ratio, but others may have a more informed idea of what works.
Looks like we will have to have a AR380 aquascaping competition soon, there seems to be a few of them turning up, mine is blue and I hate the colour, as with yours it was a second hand acquisition, complete with blue glass chip substrate as well!