frequency of water changes for betta fish bowls

We've kept bettas in 1 gal bowels doing 75% water changes every 2 weeks. But we feed our betta one pellet at a time to prevent any from rotting in crevices in the substrate. With the water change I vacuum the substrate very thoroughly. Bettas I believe don't need pristine conditions.

1 gal bowels? That's crappy.

Poking fun at the hilarious typo aside, bettas think male guppies are other bettas. That's incredibly unlikely to work. I keep mine in a 10 at 80F with some snails. He's killed some, but mostly ignores them.
 
I don't know, I'll check the water after a few weeks. If the water is good, I may just leave him in there. If it's bad, I may give him to my nephew. He seems happy, no signs of stress yet.
 
Testing daily will tell you far more than testing in 2 weeks.

Bettas can survive in horrible conditions. They'll even live a year or two.

But given a good environment, they can easily live 6+ years. That says far more about what's better for them than their ability to tolerate bad conditions. Keep in mind that ammonia levels can be toxic without causing stinky, cloudy water.
 
Whoa! After I added the plant on top of the bowl, and a few small java fern plants, the nitrates, nitrites and amonia dropped to 0.

Do you think this is because of the plants, or do fish bowls get "established" the way an aquarium does?

I've continued with regular 50% water changes.
 
Is he in half a gallon of water, or one gallon? Water quality aside, half is not enough, that's very small. There isn't much room to swim around in a half gallon of water. Even one gallon is a bit small. Keep an eye on his fins and tail, if the water quality is bad enough they will start to fray.
 
IMO, a fish bowl is so small that doing daily water changes shouldn't even be an issue. It would take all of a whole min or so to pour out half and add new, clean water.
 
And keep in mind that nitrogen compounds are just the wastes we can detect by testing. There are other waste products that build up as well.
 
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