My pH varies about .2 over a 24 hour period. Low is around 8.15-8.2 and high is around 8.35-8.4. The top and bottom drop some when my reactor starts running out of kalk, which is usually my signal to add more kalk to the reactor. Looks like yours is a bit more blunted than mine (a swing of around .14). I'm not familiar with KdH so I'm not sure what that alk means. I keep my alk around 3.0 meq/l which I believe is balanced with calcium of 410, which is where I try to keep the ca. I keep my temp right around 79.