Kind of looks like some species of glass fish (Chanda, Ambassis, Parambassis or...?)
I do what you are suggesting a fair bit, but still don't feel 100% confident with it. Freezing will likely kill all multicellular parasites like worms, but many bacteria will survive, and I don't think viruses will even notice.
There are people who sterilize everything that comes in contact with their aquariums, and they would never consider taking this course of action. Food will all come out of a hermetically-sealed can; these people boil rocks. No chances are taken.
Then there are folks who buy a bucket of live minnows at the bait shop, drag it around in the hot sun with them all day, and if any are still left when they get home at the end of the day they go into their fish tanks as snacks for their beloved pets. No s**ts are given.
I know I am being hypocritical when I quarantine new fish for literally months...and then toss a whole sunfish into the freezer for a few weeks before using it to feed my own aquarium fish.
There's evidence suggesting that children raised in a household with dogs...and the constant exposure to an assortment of germs which that entails...have stronger immune systems than kids raised like lab rats. Maybe that's true with fish as well? Hmmm....You make your own choices. Nothing is 100% safe. Life doesn't...and shouldn't...work that way.
And I'll add here that the cost of the aquarium fish doesn't enter into it for me. I may be able to replace a given fish species for a few dollars, but the individual specimen that I have raised from a pup is unique and irreplaceable. The market or intrinsic value of the fish is unrelated to its sentimental value to me.
