Went to Walmart on Friday and picked up two fans for my tanks. Check these fans. The one on the left has a build-in rechargeable batteries and you can add some more batteries if you want. The thing I like about it is the battery part. Heat is not a problem in a summer when the power goes out. It's also thinner and stronger. I also hate that part because you can't really put them on the controller and a bit noiser than the right one since it's stronger. I think everyone familiar with the one on the right. Both of them cost $12.99 each ;D ..