Ive never tried such a set up, and got away from using perlite very quickly when i started. co2 is heavier than o2 so... I'm not saying it will be an issue but if you have an issue its a place to start. a few holes right above the perlite layer will solve this. you need to keep your humidity as high as possible 85 is on the verge of low. i seem to remember people talking about a "tropic air" system. http://www.reptiledirect.com/tropicairhumidifierandairexchangernopump.aspx you can see it here. very easy to make your own with some ingenuity. ultimately as long as you have good FAE, and RH, and sterile techniques no matter how you get it you will do well.