Safe shutdown procedure and memory required

Hi Guys. I have my Raspberry Pi and Brew Pi powered with their own separate transformers, the two are linked with a USB to micro USB cable. My question is: how do i shut down the BrewPi safely, i.e. without corrupting anything? I can shut down the Raspberry Pi with the shutdown command but this leaves the BrewPi running, how should it be shutdown, is it safe to just unplug it? Whilst setting it up i had it powered by the USB to the Raspberry Pi and it concerned me that it was being shutdown by just cutting the power to it, should i be?

Additionally how much memory do i need to run the system? At the moment i just have the 8Gb SD card that came with my Raspberry Pi, is that enough or should i clone to a bigger SD card / use external storage and if so how do i tell the system where to store the data?

Advice would be appreciated.

You can just unplug the Brewpi and it will be fine. As for space the 8GB card should be fine that’s what I run on all mine and have not have any issues.