I have 11 feet by 18 inches of open tank I'm using close to 20 gallons a week in my ATO
In a closed tank I wouldn't expect you to lose that much to evap

wow, that's a big tank, 11 feet! How many gallons is that?


20 gallons ATO per week? yike :)

Tank is 125ish gallons it's 6 feet the sump is 90g and 5 feet long