So I ordered the large 2 liter bottle of rally pro and it says it treats for 400 gallons.. do i have to buy several 2 liter rally pro to keep up with the 3 day dose? I'm wondering if the number on the bottle of 400 is including the three days or is that per treatment because I have a 200 gallon tank and a 2 liter would get me 2 days of treatment if that's the case. What was your experience if you don't mind me asking.