yes im very 'overstocked' but i prefer to go by the rule of are the fish happy.
guppies are tiny compared to the size of the tank, and babies move on to other people.
i upgraded from an 8g to a 20g a couple of months ago.
1 X-Ray Tetra
1 Silver Dollar
2 Scissortails
1 BIG Common Plec
those were all 'rescued' from an 8g which wasnt wanted anymore. thats why there's a few odds and ends! the plec had lived in the 8g all his life, so he's in a much better home now, even if its not an ideal size.
i will upgrade again, when i have funds!