I just put together a 57 gallon rimless tank with a 30x15 sump. I have about 57 gallons of water throughout the sump and the aquarium itself and another 10 gallon auto top off reservoir on the side of my tank. I have had the tank set up for about 23 days now and have gone through about 20 gallons of water being added into the tank due to evaporation. Is that a normal amount for a tank to lose so much water?? I only currently have a net top on it so that will obviously be a reason for so much evaporation until i get a glass top of some sort.