sorry i forgot the question
im making new screen doors and screening the top
question is do i need to screen the sides if i install small fans for air flow
What are the sides? I assume enclosed with glass/plastic? I wouldn't worry. It will help keep humidity compared to an all mesh screen... I was thinking of doing that to my cages as I live in Canada
Depends mainly on the exact dimensions of your enclosure. When the tank is relative deep and the doors are far away and not that big a fan is not a bad idea