How often are you doing WC
's and how much do you change out each time? Part of the reason for doing a large weekly WC
is not only to remove excess nutrients but to add buffer back to the tank water (unless you have soft tap water which is quite uncommon). Right now your numbers are very good. I run my tank Gh
at 4 which is good for plants. If your doing large weekly WC
's and your readings continue to drop then adding crushed coral to your filter or hanging some in a media bag under the outflow of the filter is a good idea.