Stress coat is actually a good thing to have. My Dwarf Gourami had a scrape at the top of his head that looked red and raw on tuesday. I added some stress coat to the water that night, and the next day, the redness was gone. And now, this morning, his head had healed and scales had covered the rawness.
I have had plenty of fish heal from scrapes without adding anything at all. I heal from scrapes without anything either. In fact pretty much all living things will heal from minor scrapes and abrasions because cells reproduce and repair. That's just life.
My additions to this thread are:
Ammonia removing filter media. You shouldn't be worrying about ammonia in a tank because your tank should be cycled before you have anyone living in there who might get hurt by the ammonia!
Ammonia alert. An established aquarium will never, ever have an ammonia problem unless you've done some massive mistakes - and you would be well aware of those mistakes and hopefully be testing for the ammonia anyway!
Blackwater extract. A bag of aquarium peat will last you for the better part of a year and cost only about eight dollars; all the while doing a far more natural and effective job. Or you could buy blackwater extract that does little more than tint your water and pay a dollar per water change so that the annual cost is like sixty dollars.
Snail killer. Stop committing genocide on these harmless little creatures! And especially don't do it by filling your aquarium with noxious garbage. Do you think the other inhabitants would appreciate that stuff in their water? Deal with snails by not overfeeding, and by accepting them as part of a natural and well functioning aquatic habitat.
Many different foods are useless junk. Especially the supposedly high end ones like Hikari. They often have the same crappy ingredients and fillers than lower prices brands contain. And the foods often meant for certain types of fish (discus, oscars etc) are usually no different than the general staple flakes or pellets anyway with maybe just a few added things that those fish like. Best to have a well rounded selection of various foods than to depend on one thing.
Wet/dry filters for all but the most seriously huge and overstocked systems. The massive amounts of ammonia that require ridiculously massive bacterial colonies would only come from having your tank ludicrously overstocked.