Bettas are more likely to suffer longterm, in small bowls,jars,vases,cups etc, than they will in larger tanks with heater and healthy biological filter.Until people actually demonstrate their professed love of these fish by providing them with a proper enviornment,, there will always be the numbers of posts regarding sick bettas that are evident here and on other forums. In small uncycled containers ,water parameters , Ammonia,nitrites,and nitrates can Quickly become lethal.In larger tanks,, with mature biological filter, these toxins can be diluted by the beneficial bacteria in the filter and through water changes. The very fact that people keep buying these fish and placing them in uncycled small bowls,etc only promotes more of the same.