Hi!
I'm new to this website, and having just got my third betta fish (my other two have died from sickness and too cold water

), I don't know if my tank is large enough. I got my tank at
walmart and it's about 41 FL OZ big. It comes with a bottom and a divider since it was originally meant for two fish, but I thought that a putting two fish in a tank that small wouldn't be very appealing.
I've heard how betta fish need a tank of about 5 gallons and a filter with heater. Do I need to buy all those things? I was planning on getting a one gallon tank, would that be fine for my betta fish? Right now, he's swimming around a bit, and likes to sleep on the smooth rocks at the bottom, and seems a bit stressed out. Please help me, I want my fish to be happy and healthy! Thanks!