The carbon dose amount is listed at 3%. I put 12.5 ml in my reefer 525 (approx 125 gallons after rock displacement and whatnot). That means twice a week I would be putting in 1/3 ml of carbon source, or a few drops. I really don't think that has an effect. It would be easy for people to overdose though. Unless you have a huge tank the little measuring cups are a bit big.