I use 1/4" ( 0.22" ) Clear Extruded Acrylic Plexiglass over my 125 gal refugium. I've had to keep the pieces over the fuge more often to cut down on evaporation. However, I've notice that the corals don't do as well. I'm currently running a 6' T-5 unit with recently replaced bulbs. I've stayed away from glass as its my understanding that certain types of glass filter out beneficial light. Yet, going to a thinner plexiglass- 1/8" ( 0.118" ) leads to the material bowing and warping. Is there a better way?