1. The eheim software itself has a firmware update button, but it links to a defunct php script on their site, so it doesn't work. They no longer supply firmware updates to users, you can send in your pump head (yeah, right) or you can use a third party software from "GHL", a company that eheim seems to have an agreement with about distributing the firmware at their (GHL's) risk.

​2. I found the manual for the GHL updater and the filenames of the firmware indicate that the pump is controlled by a PIC18F252. This might be handy to know down the road.

​3. The manual also indicates that the PIC is using some kind of bootloader and there is a application note for a bootloader for this PIC on the Microchip site. Maybe eheim just re-used the code. Something to poke at later.