Barebottom tanks, lots of spares so on fish cleaning night we set up the clean tanks with water, turn the heaters on, go do something else like clean the big tanks, come back in an hour or so after the 1gal water has warmed up, net out the bettas and put in clean tank, swish their floating plants in a tub of clean water to rinse them off then put into the clean tank with the fish, put on lid, finished. (Ok, take the dirty tank and pour the water on any houseplants still living, refill the daphnia tanks and shrimp tanks, pour any gunk down the toilet, sterilize the dirty tanks for use on next fish cleaning night.) Whatever method you use, if you put your bettas in small cups or containers, put something ontop to cover the container--LOTS of people find their fish have jumped out of the small containers (someone once stepped on his fish who had jumped out onto the floor).