I use the same tubs as Deb, I like them a lot for incubating
I wouldn't use anything larger than a computer fan in a 3 ft tall incubator, the bigger fans put off a lot of heat on their own.
We tried using the fan that comes in our large true coolers and the fan alone brought the temps up to 88 degrees.
We use bathroom ceiling fans plugged into a zoo-med rheostat to control the fan speed which helps to fine tune the temps top to bottom.