According to Sera's website: "sera aqutan clears the water, immediately binds harmful heavy metal ions and neutralizes dissolved salts and aggressive chlorine. It protects the mucous membrane of the fish due to its valuable vitamin B complex and skin protecting colloids. sera aqutan is ideal for reducing stress during transport and introduction of fish. In a 45 minute bath under threefold dosage, sera aqutan is effective against acute intoxications by metal ions and ammonia."
So, is the "tan" for "tannins" then? with some yeast extract for vitamin B complex? and some sodium thiosulfate to neutralize the "aggressive" chlorine? and those colloids? are they acting as a flocculant that "clears the water?"
How could something "neutralize dissolved salts" unless those salts were bi-valent cations, such as calcium and magnesium, and the tannins were chelating them just like peat tea?
Where there's no list of ingredients, attempting to parse the mixture just from the claims made for it is dodgy at best...