Both of my current tanks have back filters with adjustable flow, to keep the current to a minimum. I have kept bettas without filters as well, and the bubble nests are more frequent when there's no annoying current to destroy all their hard work.
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It's tricky getting the temperature to match, I had two thermometers of the same make and would tweek with the fresh water until it matched, or was within a degree when I was lazy. But weekly 100% water changes were a pain in the butt when I was taking 22 credit hours as an undergrad, so I opted for filters really fast. I once had a really messy, pooping fool of a betta, (his name was George III, I was real creative with names back then
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) who needed 100% once a week and then an additional 30% in between. He was a big pig! He was the one who first got a tank with a filter! I swear he pooped bigger than my Pomeranian!
As far as temperature is concerned, my bettas are kept rather warm because it's been rather warm in IL and running my AC is not cost effective. The temps of both tanks are at around 82, which is too high for my taste, but it should gradually lower as Fall approaches. In winter, I like to maintain a temp of between 78-80 with a heater, but I like my tanks on the warm end. It can be rather humorous when the tank is at 80 and my apartment is at 60! Which happened once last year. Those were the days when I really wished I was a fish and didn't have to deal with outside temperatures of 25 below.
I've rambled on enough, hope this bit of info helps...
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