If you do not have an auto top-off for replacing evaporated water, you will have to add freshwater by hand. This usually involves some combination of a cup, pitcher or trying to ease a 5-gallon bucket full of water over your tank or sump. There is an easier way. Use a designated freshwater container that is lower than your desired top-off level and simply drop in a small pump with tubing that goes into your sump or high flow area of the tank. The key is a small pump that delivers a slow stream. If you already have a more powerful pump, attach a restriction to the output to lessen the flow rate. Instead of lifting containers of water simply plug in the pump, allowing the freshwater to run until you have reached the desired water level. Then unplug. Or you can even plug the pump into a powerstrip with a switch to turn it off and on. It is a good idea to not allow the tubing to contact the higher water level after top-off as you may create a siphon when the pump is turned off.