He is in a bowl?
A beta needs at least a five gallon tank. This is not just for extra swimming room, Small tanks are extremely difficult to maintain, And filters, heaters... made for them are poor quality. small tanks are appealing to beginners, but best left to experts, Bigger is always better and easier! 5 gallons is still small, but can be maintained.
Betas need a filter but hate current. You can use a chemical free sponge and ties it up in front of the water that flows back into the tank. Now you have low current and extra media for healthy bacteria.
Betas need a heated tank at stable temperature between 78 and 82. Get a heater with 5 watts or so per gallon of water. Get an adjustable heater, not one with a set temperature! Start the heater on the lowest setting. Because you do not want to cause temperature shock to a beta which has lived in cool water his hole life. Turn the dial on the heater up the smallest possible amount, and check the temperature in the tank with a digital thermometer every 4-6 hours or ever day. And turn the dial a tiny amount again as needed, every several hours or every day, until the temp settles at a stable temp between 78 and 82. 80 would be ideal. Make sure the temp is stable 24-7.
Never remove the fish from the tank just to clean it! Use a gravel vacuum to change 25% of the water once a week while sifting through the gravel. NEVER DO A 100% WATER CHANGE!. "unless there is some sort of contamination/emergency." Add new water that is the same temperature as the tank water. Add water conditioner to the new water. Prime is the best water conditioner, it has added benefits , It takes 2 drops from any eye dropper to treat one gallon of water. it is safe to round up if you are not sure. A liitle more is better then a little less.
Feed the fish about 3-4 pellets a day. New life spectrum beta pellets are the best. Many "betta foods" are full of junk that betas can not even digest, stick to the good stuff omega one is pretty good for flakes, and new life spectra for pellets. feed thawed out frozen brine shrimp, blood worms, or daphnia, at least 2 times a week. Use a sharp knife to safely get the equivalent of 3-4 beta pellets from the frozen block. Then thaw it in a small cup of the tank water.
Decorations are important, but also should not take up too much swimming room, Never block off the water surface either. Bettas need to easily get to the water surface to breath. Silk plants or live plants are good, but plastic can rip fins. Broad leafed plants are great and can be used by the beta to rest on. hollow decorations with a wide opening will be used by your beta.
Beta fish are aggressive to other betas, and to any fish that they mistake for rival betas. But in a tank of 10 gallons or more , betas can live with carefully selected species of calm fish. Just be careful to observe your fish, they are individuals, and not every beta will tolerate other fish, and not every fish will tolerate a beta.
The problem I had with betas in a community tank, was the beta not getting his fair share of food. I often spot fed him with an eye dropper, He Had more success in a tank with less active fish.