The most likely cause is a processing residue or packaging-related off flavor , not chlorine in a dangerous amount. Fish processors sometimes use chlorinated water for sanitation, and the scientific review I found says exposure from properly processed seafood is generally very low and not considered a public-health issue when good manufacturing practices are followed.

What that taste might be

A chlorine-like or “chemical” taste can come from a few things:

  • Residual sanitizing water used during processing, which can leave a faint off-note.
  • Packaging or storage issues that make fish pick up odd flavors.
  • Fish that is starting to degrade, which people on retailer forums often describe as “off,” “chemical,” or “ammonia-like” rather than simply fishy.
  • Different sourcing or handling between stores, since shoppers report mixed experiences with Aldi salmon while others say it tastes fine and is comparable to Publix.

Is it healthy?

If the fish is truly just mildly affected by processing water, it is generally not considered harmful at the levels used in seafood processing. But if the salmon tastes strongly chemical, bitter, sour, or ammonia-like, that is a quality warning and you should not eat it.

What to do

  • Check the sell-by date and keep it very cold.
  • Open it and smell it before cooking.
  • If the odor is clearly chemical or the texture is slimy or mushy, discard or return it.
  • If this happens repeatedly with one brand or store, switch sources, because handling and sourcing can vary.

Practical read

A little difference between Aldi and Publix salmon is believable, because forum reports suggest taste and texture can vary a lot by batch and product line. The safest rule is simple: mild, clean, ocean-like smell is okay; chlorine, ammonia, or paint-like taste is not.

If you want, I can also break down how to tell whether a fishy taste is normal salmon flavor versus spoilage.