We´re having boiled cod for dinner, can the goldies share our meal??

I wouldn't. If you are anything like me, you don't wonna eat your fish completely saltless, or without any kinds of herbs on it. And thats exactly what the fish would need if you consider feeding them human food - nothing with any kind of spices.
If you want, you can add cod into a mix of gelfood though, as the protein source, together with some veggies and gelatine.

YOu could always take a little peice and cook it seperatly.

I typically take a small bit and rinse it off to get all the spices and junk off it before I feed it to them.