So I have a 5 gallon tank that isn't filtered. I don't plan on getting a filter. I read that they aren't necessary is that okay? Anyways, I do 100% water changes every week. But I read that they are a bad idea. I acclimate properly everytime. Are they okay to do?

I'm sorry if I missed this anywhere else, but I need advise on 100% water changes- I'm just really afraid I'll shock my bettas when adding them to the new water. I let the new water from the tap set in a bucket so it becomes room temperature and decholinate it, and I have containers I put...