Fan, Temperature & planted tank

[raytan12]

Which brand of fan is suitable and safe for use on planted tank?
how much can the temperature be reduced by using a fan?

[sherchoo]

Suitable fan? If it blows and tank gets cooled, it should be suitable. How much it cools depending on tank size, ambient temperature, room ventilation, fan size, position of fan, lighting condition, tank covered or not... etc. Too many conditions, but generally a normal 4" AC fan can cool up to 2~5 deg difference.