IME, I've used it to cool down my 1.5 x 1.5 x 1ft IOS office tank during the weekends when the A/C is switched off, and it is able to achieve less than 28oC. My office is completely enclosed, so it is definitely warmer than our homes (assuming you open your windows), so I'm surprised that it struggles to cool a 1ft cube. What temperature are you guys running your tanks?