2.5 gallons for Mr Melinko, 10 or so gallons for Erick though Snowball lived in a cut up gallon milk container while I was in the process of moving lol
i have them in 5 gallon, 2.5 gallon and a 1 gallon- and yes, 1 gallon is small, but i didn't mean to come home w/ 2 bettas- so she's waiting til i can afford a larger tank.
Max was originally in a 1/2 gallon - then I moved him into a 1.77 gallon. I have just bought a 5 gallon tank with a filter... that will be his new home as soon as I can get some BioSpira to start the cycling up.
I have kept single bettas in 10 gal, 6 gal, 2.5 gal, and 1 gal. Right now my only betta is in his 6 gal. I'll probably get two more bettas and house them in the 2.5 gal tanks.
My guy's in a 2.5 bowl with heater (and he's still not eating!) and I just ordered a 3 gallon new pico tope tank with filter and light. I'm so excited! I just have to find a place in my bedroom that's not in direct sunlight or I have to keep adjusting the blinds!
We also had one in a 10G, 3g and one of those round bowls which was probably about 1 gallon--got him out of there pretty fast--too cramped--now I just use for water changes.