Is it okay to freeze fish at home, after it was only refrigerated in the supermarket?
This is a relatively common practice in my household, no harm has come from it to date, but do it at your own risk.

One may say "Why buy fresh fish and freeze it, just buy it frozen instead, it is probably a lot fresher", but at least where I live (Portugal) there are a few reasons to buy fresh fish and freeze at home. Just to list a few:


It is still generally relatively fresh even compared to pre-frozen packages, and you can get a lot more different varieties and species than you could from the pre-frozen selections alone.
You get to see the whole fish "live" and unspoiled and easily assess it's quality, size, freshness, and characteristics etc.
Unfrozen fish can also be cleaned up a prepared at the supermarket by the staff to your desire, which is unavailable for frozen items, and saves some trouble and mess at home, while being prepared by professional, or at least trained staff.


Flavor and texture should be well preserved, suitable even for more delicate preparations like grilling, as long as you don' take too long before freezing it, or store it for very long periods in the freezer.

Just make sure it is actually fresh fish, here local supermarkets specifically label store thawed fish for immediate consumption, and often verbally advise the customers at the moment of acquisition to not re-freeze.