Hey,
As Jan already suggested, if you’re making changed to theme files, please do so in a Child Theme. It’s kinda easy to setup.
Alternative way: use a plugin. Actually, I’ve never used one, and can’t really recommend which one would work the best. If your installed plugin breaks the layout, please provide me with a link, so that I could see what’s the problem and might suggest you some fixes.
Alternative way #2: if you have FTP access, just drop in favicon.ico into /public_html/ and /wp-content/themes/pisces/ ?? It should also do the trick ??
If you have any further questions, or you would want to provide me with an URL / login credentials, feel free to shoot me an email at [email protected]
Tom