Gold Barbs, also known as Chinese Barbs, as in Puntius semifasciolatus?
In many homes these can be kept in heaterless tanks that change temperature through the seasons, providing the temp does not dip below 18C too often and on average the temp is less than ~22C (with a "summer season" of upto ~24C). They are temperate, not tropical fish, keeping them at mainstream ~24C tropical temps all year round is not good for their health or lifespan.
These barbs, like many other barbs, do far better in 10+ groups (something that equally applies to many other social fish). This will also increase the odds of there being multiple males in the group, which will more likely enhance their colours and you will get to see the males competing with each other for the females' attention.
The "obvious" choice for another upper water group would be Zebra/Leopard Danios or White Cloud Mountian Minnow, that again are temperate fish. These will give the barbs some confidence, but again the danios/minnows need at least six but ideally 10+ in their group.
You could do 1 or 3+ gourami (to spread aggression in their own group, with other one male). You could even try a single Paradise Fish, but these are a bit territorial and can eat small tankmates, so let the others grow and settle in before adding one of these.
Peppered (better if you entertain a Paradise Fish as these catfish are bigger) or 3-lined Corydoras would work well if the tank floor has fine sand.
I quite regularly comment about temperate fish species on here, there are far more than many keepers realise and so you might fancy something I have not mentioned here, which is a merely dip in the ocean in terms of temperate fish.
Edit: There are the odd tetra species that are temperate, for example Buenos Aires, but they are infamous nippers to tankmates and real plants.
