What is the proper smell of Basa?
Basa is in the catfish family (http://en.wikipedia.org/wiki/Basa_fish), so it shouldn't require any special treatment.

Buying frozen fish, even from different stores, you may be getting it from the same supplier.  Perhaps it's something the supplier is doing, some kind of preservative treatment or something of that nature that your husband can taste, but you can't.  Check the ingredient label on one brand that you've purchased before and look for what was used, if anything, to treat the fish.  Then, assuming something was used, seek out a different brand and check its label to see if they used something different.

Now, all that being said, I've purchased Basa from the seafood counter before.  Coming from Vietnam, it had to have been previously frozen, but it had no real scent at all.  After you defrost the fish, it should have very little scent.  A strong "fishy" odor just means you have old fish, and perhaps he's picking up on some funky compounds in the old fish (some people are much more sensitive to bitter flavors than others).