Thank you. I had previously read the post you linked and wasnt sure exactly how to test ventilation. I will test ventilation in a little bit. I do have vent holes in my tubs but just a few. after testing I will add more if necessary. My 41qt racks also have a 1\8 inch gap between the shelf and top of tub. hatchling tubs fit snug but havent seen any issues within the hatchlings ever.