its simple. warm water results in evaportation. its normal for your tank to lose water due to evaporation as you can see from a lot of peoples replies. a way to solve this is to add a better lid with less room to escape or turn down your temp (which I DO NOT recommend). also.... if you have a sump, you are going to lose more water out of your sump that your tank because most sumps dont come with a lid. hope this helps
