I would like to know the same thing - how to reset my logs, to start from scratch as it were.
But Alan's guide is up to version 20 now, and this answer does not appear on the pages noted here. In fact, I've searched the document for the word log, and how to reset logs (other than update firmware or add modules) does not seem to appear anywhere.
My problem is that I loaded the new firmware a few weeks before I installed the apex. So for weeks my pH and temp probes (which were in even plugged in, much less in my tank) recorded near zero readings. And now that I've installed the Apex, that's graphing. And it's not so much that bad data that bothers me, it's how it messes up that graphing scale. I can't even see the temp fluctuations in my tank (on the graph) because not only is it plotting the 79 degrees the tank's at now, it's plotting 20 degrees for the weeks when the probe was not even plugged in.
I tried re-updating the firmware. But the Apex was not fooled. The firmware updated alright, but did not reset the graph. I guess it knew I was not "changing" the firmware. Just reflashing it.
Anybody know how to the the "reset" button for logs on an Apex?