What fish would be best for this tank?

[Olympia]

Celestial Danios/Galaxy Rasbora are cold water and I believe you could have a small school in a 10 gallon, as they stay small :)

[Fin2you]

heater & more options! If I could I'd send you my spare heater!
I personally love Cory's as Betta tankbuddies!

[thekoimaiden]

Celestial pearl danio could work, but the males can be kinda nippy. They also might need a heater as they like temps between 68F and 79F. You can read more here Seriously Fish - Celestial Pearl Danio (Danio margaritatus) and here TFK Profile on Celestial Pearl Danio (Danio margaritatus)

Personally I vote to spring the extra money and get a heater. It's really going to open up your choices from stuff that just barely fits in a 10 gal to stuff that really can fit in a 10 gal.

[Olympia]

^ I do agree with that.

[betta fish crazy]

I I do get a heater, I'm think of having a tank with 1 Platy, 1 Dwarf Gourami, and 3 Guppies. AQAdvisor says:
Your aquarium filtration capacity for above selected species is 110%.
Recommended water change schedule: 31% per week.
Your aquarium stocking level is 78%
If I try to add more fish my aquarium filtration is not satisfactory. Is this a good setup? Will there be any aggression issues? Anything I need to know? I've heard about the male to female ratio with guppies. I think that this tank will need to be kept at about 73-77 degreesFarenheight, does that sound right?

[Bombalurina]

I'm not a fan of dwarf gouramis in ten gallons. They get to be 3 inches long and can be aggressive. I wouldn't advise one in less than 15 gallons. Try looking at a honey gourami instead.

I'd also advise against having just one platy. Like guppies, they are social fish and should be in groups of 3 plus.

[Olympia]

I'd go with either 3 platties or 3 guppies in that case.

[betta fish crazy]

Will there be agression between the guppies and the gouramis? Also, is a honey gourami what PetSmart calls a "honey sunset gourami?"
It says here they grow up to 4 inches:http://www.petsmart.com/product/inde...ductId=3954125 Are they less agressive than the dwarf gouramis? Sorry to be asking so many questions but I didn't know I would be thinking this seriously about a tank with a heater. According to AQAdvisor, I can keep a honey gourami with 3 or 4 platies and have enough room. I can also keep a honey gourami with 3 or 4 guppies and have enough room.

[MaisyDawgThirteen]

I'm not sure about other's guppies but mine 4 out of the 5 of mine are really nippy. :/

[Olympia]

Yes that's a honey. They do get a bit bigger, but they are less active, and tend to be more passive, less likely to chase around other fish.
I also hear a lot about dwarf gourami being prone to a species specific illness since they were badly bred in the past..