If I were you, I would leave it open for three very important reasons!!!!
One, by covering up your open space at the top of your tank you cut down on the amount of light into your tank!
Two, you increase the amount of heat generated by your lights etc. and that could heat up your tank water.
Three, you cut down on the air surface interface-the gas exchange>CO2-O2 from tank to the ambient surroundings!
Hope this helps! _________ 125gal.w/Mag9.5 return(dual megaflow)>Mag7 pump Aqua Cev180skimmer.Wave2k Hamilton Reefstar(2)250watthqi(mh)pend.a Yellow, Naso Tang Red Lip Blenny Percula Clown Demoiselles Niger Trigger F. Wrasses Ceriantharia Orn.Shrimp and Stars Hermits Queen Conch asst. snails> Stars Zoos shrooms Montipora Brains Gorgonians Favia Turbinaria(large+small polyp) Acropora Xenia Tridacna (CroceaMaximaSquamosa) Leathers <35+75gal.reef tank as well>
"IF THE PHONE DOESN'T RING...IT'S ME"  jb |