He looks pretty healthy. To keep him that way, make sure you definitely do get a heater! You'll need to find out what size the tank is so that you can get a heater with the correct wattage. 
You'll also need to do two water changes a week - one 50% change and one 100% change.
I see you have a betta leaf hammock in there - does he have anything else? A plant to play with or a cave to hide in? Bettas are curious fish who really benefit from things to interact with and hide in.
You'll also need to do two water changes a week - one 50% change and one 100% change.
I see you have a betta leaf hammock in there - does he have anything else? A plant to play with or a cave to hide in? Bettas are curious fish who really benefit from things to interact with and hide in.
