So my mom brought a betta fish home two days ago because the previous owner is no longer able to care for him due to health issues. She had been keeping him in a small fish bowl and he looked miserable. He was doing very little besides hanging out at the bottom of the bowl, probably due to the fact his water was way too cold. I moved him up to my bedroom and I've been slowly adjusting my space heater so his water will (hopefully) warm up a little bit. He's perked up some but this setup is obviously far from ideal.
I have an old 29 gallon tank (30 x 12 x 18) (along with a filter and heater)
I'm wondering if it's too big for him. Should I buy smaller tank or go ahead and set the big one up? I'm worried it might stress him out.