Ive just recently purchased a beta fish and i was wondering when i need to do a water change. i have a 2.5 gallon tank and different sources say ifferent things. some say partial water change weekly some say full water change. please help. and also how often should i feed it? and any other advice would be helpful.

also should i turn off the aquarium light at night? should betta fish be in dark at night? thank you