I have set my DOS up to do auto water changes. I am having a hard time deciding between 2 gallons a day and 3 gallons a day. The system is 120 mixed reef with a 20 gallon sump and oversized skimmer but I do not know the exact amount of water in the system. So basically 14 gallons a week or 21? I may adjust the amount of days it runs due to refilling and mixing time but the gallons per week will stay the same. Thanks.


