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Fish bowl is wrong to begin with for fish keeping.
No fish bowl is big enough to hold bare minimal water for fish, and its shape is also not good for gas exchange between the water and atmosphere.
Minimal tank size for keeping stable water conditions is 5 US gallons. Ten gallons is recommended.
(However, for goldfish, this rule does not apply. Goldfish are messy eaters, they grow to very large size and they produce tons of waste. Bare minimal for a single common goldfish is 40 gallon, and 55 gallon is needed for two. If it is fancy goldfish, then 20 gallon is the bare minimal for just one, 30 gallon is required for two).
A filter system is a must and it must be running 24/7 as long as you keep fish in the tank.
Water change in a well maintained aquarium should be done once a week and it should be called "partial water change". It is recommended not to change more than 30~50% of the total water in order to keep the water temperature, hardness, PH, etc. stable. Too large of a swing in any of the readings I just mentioned could shock and even kill the fish.
We have plenty of beginner articles for fish keeping in our library section. It can be more helpful if you read through them.
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