I always take my fish out when doing water changes over 25%.
Less stress and less likely to get injured.
Florescent bulb on the lamp is best.....plants have a hard time with incandescent.
DONT FORGET YOUR HEATER!!
I have a 5gal...no filter....100% water changes a week with water skimming every day or every other day (with a cup)
Plastic plants shouldnt be sharp....they can tear betta fins more so then other fish fins. If a pantyhose can get snagged by a part of your plant so can a betta fin.
Its so much fun having a betta! Your going to LOVEEEE it!!! Watch out or in no time u will have two or three....its an easy addiction! LOL