Temp is 20-30C with 25-28 being optimum. Feed them a high protein diet with some peas or lettuce occasionally. No matter what people say a betta needs at least a gallon, with 2 or 3 being preferred. Anybody who tells you bettas hate large tanks is lying. I personally think anything more than 5 gallons or so is overkill because some bettas don't get on very well with any other fish at all and so you end up with a medium sized tank with one fish in it, not very interesting. But they can live in large tanks. Some even live in big communities. Suitable tankmates vary from betta to betta. Cories are usually tolerated as are small peaceful tetras.