Since you didn't list your setup...Put a full cover on your tank and a full cover on your wet/dry sump. Place 1 airline to add fresh air to your sump, reduce your temp to 78-80F, Stop using any bio-wheels, and you should see less evaporation.
make sure the glass top is covering the tank. Large cut-outs for filter tubing or heater power cords ruin it for you. Cover your tank thoroughly, that will solve your problem.
Ditto. My 125 has glass lids with fluvals for filtration. very little evaporation. My 55 with plastic covers and two openings for HOB filters loses more to evaporation.