Truck
UKAPS
I'd love to know where that statistic came from, The temperature in the wild fluctuates all the time, by at least +/- 3oC per day.
Not to be rude, or sound rude, but where did you get your statistics as well? (See, it just sounds rude... lol )
Uber-vast amounts of water can retain temperature quite well. And plus, these are bred bettas, not wild bettas. It's no surprise a wild betta would completely dominate a bred betta if they were to ever meet and fight. Wild bettas have the actual adaptations for that, as bred bettas just have the instinct.
You're right in saying water holds temperature well, but when it rains it can drop rapidly, it will also drop at night, I read it in a paper that was published on the paddy feilds in which betta's are found, it's pretty common to all fish habitats.
And also, Bitteraspects makes a good point, keeping fish in a 1G is definitely possible, Dario dario is a fantastic species to keep in a tank that size, as are other small fish.