I have the liter meter doing just top off right now. With Christmas coming I might buy the water change module and a second pump to pull water to the drain. This will alleviate the need for my to carry water upstairs and it is just around eight feet so the liter meter will have no issues. I figure I can set it for roughly 15 gallons a week and watch the parameter to see how much of the three part I will need to add. I am guessing with hte water being exchanged like this it will decrease dosing some.