I've heard people on betta forums discuss ways of keeping them warm when you don't have a fish room. The method that seems to be popular is as follows:
Get a large plastic tub, but all the jars in the tub. Fill the tub with enough water that the jars are 75% covered. Put a heater and powerhead in the tub. Now you have warm, circulating water that will keep all your fry happy.
Get a large plastic tub, but all the jars in the tub. Fill the tub with enough water that the jars are 75% covered. Put a heater and powerhead in the tub. Now you have warm, circulating water that will keep all your fry happy.