From a couple posts I googled, and though dated I believe still pertinent
2011.08.19
The blinking LED at the back of the aquaero has no special meaning. It was required for internal use when the firmware was in development. As long as it does blink in any way everything is OK. You have to worry when it is completely off
2012.06.08
Yes, that LED was used for the development process as feedback for some CPU relevant stuff. It has no real function now. As long as it blinks in some way everything is fine