i used that fan b4 for my 2 feet tank .
it is super powerful , similar to profantec fan .
but using it after like 5 months u will heard strange irritaing rotating sound .
but for 24 dollars ... it's a value for money stuff
luckily my chiller is small , CL280, didnt experience electricity bill increase by a lot ... but for bigger chiller like CL650 and above , definately , a lot .