In my basement I keep many fish tanks ranging from 20 gallons to my 270 gallon. I have noticed that I am loosing about 15 gallons of water a week from my 270 gallon as well as significant amounts of water from all my other tanks. My roommates have started to complain that the humidity in the house is getting out of hand and need to be controlled. All my tanks have lids on them fully covering all but the a 3" gap the runs the length of the back of the tank for cords and filtration. I was keeping my tanks around 80 and the house is at 68. I lowered the temp on my heaters down to 75 tonight and have a and just plugged in a dehumidifier. what else can i do to slow down the evaporation in the tanks and lower my humidity in the house. I am going to be putting plastic wrap over the 3" gap tomorrow when i can get to the store so hoping this will also help. Tanks are all fresh water sept for a 55 gallon thats salt.