I saw this post and thought I'd post what I replied to on another post. It's everything I do.
Water Conditioner I use is Prime (Best in my opinion a bit spendy but it lasts for a while. Cost for a small bottle is about 6.99, Big Bottle 8.99. Bought at Petco.) Pour a couple drops into tank after every water change.
I also keep my bettas in 2.5 gallon glass tanks ($14 at Petsmart over where I live). (I have 4 of these guys.) Except for one that is in a 1.77 but he's a small male (wasn't power grown) eventually I'll be switching him to a 2.5 glass tank. (I read you kept your's in 4 gallon nice job he'll be really happy XD!
I have at least 3 SILK plants (never use plastic it can rip their fins apart) in the tank with plenty of silk leaves on the plant so it provides a good hiding spot for him. (They live in Thailands Rice Patty Fields so it's heavily planted as you can imagine.) If you want to get into keeping live plants. Like Java Moss do some research. Live plants are even better for these guys but silk plants are good as well. (Petsmart has a 3 pack. 2 - 6" plants, 1 - 8" plant. for like 12.99. Petco has some good single plants as well.) Java Ferns are also good as well ^.^.
I use marineland 10 watt heater uses for 2 to 3 gallon tanks ($21 Petsmart) for these tanks. It's submersiable and auto shuts off when the water reaches temp. 78 Degrees. (They should be kept at 78-80. 82 for when the fish is sick.) The brand is very high quality.
Gravel/Marble is optional but not a must to have in tank. Some people say differently but it's up to you. It's nice to look at though ^.^. 3 Tanks of mine don't have gravel the 1.77 has marbles in the bottom.
As for food: HBH Betta Bites DF uses, Top Fin Color Enhancing Betta Bites is what I use. Their happy as can be ^.^. Reason why I don't use flakes is because you can easily over fed your little guy. More experience people know how much to feed them. I feed my guys 2 pellets in morning 2 at night. I fasten them on sunday.
Oh yeah and when u do water changed float the betta in the cup you got from the pet store so he can get used to the water temperature. I do this for about 10 mins then pour some water out and fill in water from tank into cup (I pour about half the water out.) Do this twice. Let sit for 5 mins each then gently pour the little guy back into tank. (I remove my guys cause I dumped all the water out and wash everything then add new water in that way I know everything is clean and no fungue and such can grow which causes my fish to get sick.)
Also fish meds. I suggest keeping them on hand in case he gets ick, velvet, fin rot and a few others. I can give u a link that explains the diseases/fungue fishies could catch.
Anyways that's everything I do. If you'd like to see how my aquariums are setup I will gladly post pics from my 4 aquariums I own.