hope this explains it better for you.if you look at the top inside right corners of my tanks you will see a white guard on bottom tank,then a black on middle tank,then white guard on top tank.there are either 100 or 200 watt ceramics in each odf the guards.as said my local reptile shop has over 100 tanks,all stacked 4 high.my tanks are 3 high.never heard of any problems regaurding these set ups.it costs roughly £50 for the bulb,guard and bulb holder thats $73.5 in your money pal.

in the picture are 2 4ft tanks and a 3ft on top.
cheers shaun