If you use a canopy, you will be happier with an enclosed canopy, with just a fan pushing air in, and an exhaust hole on the other end for exhaust. These can be screened. If you have too big of an opening or the whole back is open, it wont cool well. That is why pendants or open back canopies heat up the tank. Unless you have a fan blowing across well, they heat up the water. Oh yes, you must insulate the top too, or it will be a heat sink, and heat up. I use Celotex 1/2" foam with foil covering. Glue on with liquid nails, and seal the joints with aluminum foil duct tape- the shiny kind. Do the whole top inside. This reflects light back, and also doesnt allow heat to stay in the top, it all gets pushed out. Good luck. It34 I work at Sarasota Fire Dept Sta -3 out at St Armands 20 + years now. I met one of your rookies down in the Keys last week- Chris who has 1 1/2 years on. Steve.