Whats the best file to add meta tag to - need it to show up in activity page on bp

I'm doing a language site for a teacher. I suppress google translate offering to translate the Spanish back to English with a meta tag by doing a global site include in each student's site but can't seem to find out where to put the meta tag to ensure that the Activity page generated by BP gets it too.

Please give me some tips about how to find the right file for this (teach me to fish), or just throw me the fish: point me to the right php file to drop in this magical meta tag:

<meta name="google" value="notranslate"

Again, the only page I'm aware of that is NOT getting this is the Activity feed page at baseurl/activity.

Thanks in advance!