Fish are often described as having scaly burnt skin. This condition is generally due to the local water municipality doing a “chlorine pulse”. Since the chlorine has also hit the gills, the fish need to be treated by heavy aeration. Dropping the temperature also helps.
This condition is rare. At the chlorine concentrations that do this most fish simply die. This condition is also easily confused with slime coat syndrome. If one finds a fish like this one should also treat for slime coat syndrome. Here is a link to that syndrome:
The author, David Bogert, is a certified chemist, something that is only useful in the sections on chemicals such as conditioners and fertilizers. He has about 43 patents, mostly in the medical device field, which only helps with some DIY designs. But he also spent much of his life as a scientific researcher working on literature research, data analysis, statistics, and a little-understood field called “experimental design.” This experience is very applicable to ALL fishkeeping science. The author has been keeping all kinds of aquariums and all kinds of fish for over 54 years. He currently has ten large and many small aquariums. But note that he is not an “expert” in all aspects of aquarium keeping. The ecology of an aquarium is far too complex for anyone to be a true “expert” in all the different aspects. One can only search the journals and books for relevant research in each individual subject.