Tilapia will try to eat anything, so I'd be worried about styro. They never bothered the bubble wrap. Bubble wrap is a heck of a lot cheaper and it lets light through. Easy to cut too.

hey badflash i was at the local college,cheyney state univ. and they use the styrofoam boards for insulation and grow bed on there set up. the type of styrofoam i believe would be the issue. the boards are like expanded foam not the crumbly stuff that gets and goes everywhere.

wolfracer your an inspiration that's some good looking effort you've put out there. it was about 27degrees out here yesterday morning and i liked to froze my fingers off loading 176 cinder blocks on a trailer while the sun rose.the tires on the trailer looked like your truck coming from the quarry,by the way thanks for another great idea. one more trip like that and i'll be ready to start the foundation for the greenhouse.