I do water bottles for more than one reason. I am one of those that are always opening up my bator door so like someone previously said it helps to re stabilize the temps inside once the door closes back up. Also when my tubs get a lil dry I use water out of those bottles to put water back into my vermiculite to raise the humidity back in the tubs. Since the water in those bottles are the temp I need inside the tubs no need to get tap water and try and feel for close to temps. I use a mini office space heater with a built in tstat and fan and it works great it just takes a little tinkering to get to the temp desired.