I have a female beta in a 1.5 gallon filtered bowl. I know this is way too small so I'm upgrading to a 5 gallon but it's not ready yet. None of my betta tanks are heated because the texas summer kept them at 82-84 degrees all the time. A cold front came in yesterday and when I checked the temps, they had all fallen to 71 degrees over night. I will get heaters today for the 10 and 20 gallon tanks, but what can I do for my betta in the 1.5 gallon? It's too small for a heater but I don't want her to freeze. I can't move her to the 5 gallon for at least a week or 2 because it's already occupied. What should I do for her?
Also how many watts per gallon should I get the other heaters?