how much top off water do you use?

[Aquattro]

No idea as mine is now automated, but when it was manual, running MH lighting, about 5g per day.

[michika]

I have an approximate total water volume of 550g and my tank needs about 2-3g/day in the summer and I'm thinking a bit more in the winter, around 4g/day.

[LoJack]

144 gallon display, 50 gallon sump

I use about 3 gallons a day

Mine is low because as others have mentioned, surface agitation increases evaporation.

I use a Beananimal overflow so no bubbles and my skimmer vents under water so again ... no bubbles. I have virtually no salt creep in my sump and area.

[Proteus]

I use about 8 gallons a week on a 24"x24" tank.
While the wife's jbj with 150 halide is 2/3 liters a week. But it's covered

I'm expecting my volume to double as this week I'm putting halide back on my tank

[The Guy]

approx. 1.5 g per day 90 g tank with a 50 g sump glass covered DT tank

[Dearth]

I have a 20 gallon garbage can for my ATO I fill that up once a month for my 95 gallon tank