Hey y'all! I just purchased a water filter/bubbler for a 2.5 gal. tank with my crowntail and black mystery snail. Should I still periodically do water changes even with the filter?? Does the filter remove ammonia and all fish wastes that harm my guy?? And if I still do need to do water changes, how much water change and how often???
Thanks!
Yes, you should still do water changes - 2 50% changes per week. During one of these you should vacuum the gravel.

A cycled filter will convert ammonia into nitrate, which is less harmful but does still need to be removed. Your tank won't cycle properly, so this process may not happen fully all the time - some weeks it will, some weeks it won't. However, as has been pointed out, there are still advantages to having a filter.
Live plants will help, but unless you want to do a full on soil-based NPT, I wouldn't return the filter in favour of them.