In all my years of living in Japan and the year I spent in Korea (in the field 9 months out of the year driving through the country side and hiking) I have never ever seen any rice paddies even 1/10 of what is displayed in that image. This is a case of people exaggerating in the opposite extreme of the common exaggeration of betas living in puddles.
The ones I have seen, walked through, and helped pull a humvee out of were fairly large bodies of water compared to an aquarium but hardly even 1 foot deep and quite muddy/murky. I would guess a wild beta which can survive in the fertilizer saturated water would be quite hardy indeed....I could barely survive being within 200 feet of a rice paddy (dependant on the type of fertilizer used).