Had to dose 15ml of each today. (mag, cal and alk) I'm basically dosing my guess at my tank volume 20 gallon tank minus rocks sand all that jazz. I'm guessing maybe around 15 gallons. I'm thinking 15 ml is going to be my daily number. Just a guess though. Still want to check it for a week or so. See if that's consistent. What's a normal alk drop within 24 hrs? Any ideas? Also since I'm dosing manually, thing is due to my work schedule I dose go to work, by the time I get home lights have been out for like 4 hrs. I know testing for pH when the lights have been out will effect the outcome. What about the 3 I'm testing for? Is it ok to test for them after lights out our will it mess up the accuracy?