Besides being able to keep the danios, having a bigger tank will let you have more guppies and other fish as well.
Glad you went big and kept the danios, I like the idea of having the 10g as a QT tank. Good luck! 
On another thread, you posted something like this, about how it's better to keep fish in small tanks with innapropriate numbers than to let them "stay in overstocked LFS tanks or in some kids bowl".
When my favourite fish store got in about 100 dwarf rasboras, they were all in the same tank. They had very good filtration, daily water changes, lots of plants and lots of space (we're talking 1/2" fish).
The majority of fish are in the dealer's tanks for a short period of time, in which they get frequent water changes, many schoolmates, and are sold to people who have decent to beautiful tanks. Not many dealers allow a kid to put 50 danios in a 1/2 gallon bowl.
I'm sorry if I just derailed a little, but I find it hard to stand by as someone tells another person it's okay to keep fish in too-small tanks in too-little numbers, because they would get worse treatment if you didn't give them bad treatment.


I keep 2 danios with 2 tiger barbs. And yes the danios are natures hyper fish. I think there fine in a 10g....... always better than the overstocked tanks at the LFS (local fish store).
On another thread, you posted something like this, about how it's better to keep fish in small tanks with innapropriate numbers than to let them "stay in overstocked LFS tanks or in some kids bowl".
When my favourite fish store got in about 100 dwarf rasboras, they were all in the same tank. They had very good filtration, daily water changes, lots of plants and lots of space (we're talking 1/2" fish).
The majority of fish are in the dealer's tanks for a short period of time, in which they get frequent water changes, many schoolmates, and are sold to people who have decent to beautiful tanks. Not many dealers allow a kid to put 50 danios in a 1/2 gallon bowl.
I'm sorry if I just derailed a little, but I find it hard to stand by as someone tells another person it's okay to keep fish in too-small tanks in too-little numbers, because they would get worse treatment if you didn't give them bad treatment.