BTW, depending on how you supplement your ca/alk, you may want to keep the numbers closer to the higher end. If you have automated and metered kalk dosing and/or a ca reactor, you can be fairly safe keeping it to the lower end. But if you do a daily 2 part or other type supplementation, you can yo-you below NSW levels. i.e. if you use 1 dKh per day and you keep using 2 part to take it back to 7, then you will be averaging 6.5 throughout the day.