Upgrading To A 10 Gallon Tank

[WeeThreed]

Hello!
I have had a 5 gallon tank with a couple of male guppies that have done very well for the past year but I am finally thinking about upgrading. I only have room for about a 10 gallon tank and a stand and I was wondering after I have successfully introduced the guppies what other fish I could add. I have read neon tetras do well but I am wary of those because when I find them at pet stores they are always sick. 
Thanks!

 

[Brodeur30]

Neons are typically kept in groups of at least 6 so you have to keep that in mind. It all depends on what you're looking to get out of this tank. If you want numbers then stick to guppies and similar sized fish, but another option would be to add one or two larger fish. You could also add fish that occupy different zones of the tank   

 

[Jeremy180]

I'm guessing that since guppies have done very well, you have water that's either slightly or very hard, which neons will not tolerate.
We need to know exactly where we are on ph and preferably hardness to give you any useful information.
Also, any other fish would have to tolerate, or more disirably, prefer whatever temperature you currently keep the tank at.
Edit: When upgrading, move your old filter into the new tank to preserve your good bacteria (don't leave it off for more than an hour!)
Otherwise, you will be doing a fish-in cycle (highly stressful to the fish)

 

[WeeThreed]

The ph is around 7 and the water is very hard. Thank you for the replies!