some of us keep the betta's in the tank's when we do the water change's, some betta's (my Jasper mostly) got really mad (he got really pale and was attacking the sides of the cup) at me when I cupped him to do his water change's, he prefer's to stay in his tank..during.
so u can leave ur little guy in his tank (it's less stressfull on them and u *lol* what wiht the chassing with the net and all).
although I do partial water changes, so if u do 100% water changes someone else might want to give u advice.
goodluck with ur little guy!!