no they can't see it 2 levels down, but if you have thin walls to your basement theres a chance. But you're saving grace is that the basement is the coolest level in a house, more than likely its stays a few degrees colder than the upper levels. So everything will appear completely norml. (been growing in my basement for decades, no problems.) Also if your still worried about it they have a handy little product called polyshield. Check it out.