IMO the best place for Stress Coat is in the toilet. Do a couple of decent water changes and do not use the marine stuff for sure. But I would not put the FW one in my tanks even if you offered to pay me to do so.
I have well water and do not use declor in my tanks, However, I do use it when I bleach plants which I have to return to the tank when finished. I also brought it with me when I sold either from my hotel room or in the vendor room at weekend events. There I had to use hotel tap water.
I have a bigger bottle of Amquel (or Amquel +) and a smaller bottle of Seachem Prime.
Stress coat contains Aloe Vera and I do not want that in my tank water. What is below is why I fell that way.
Harnish, R.A., Colotelo, A.H. and Brown, R.S., 2011. A review of polymer-based water conditioners for reduction of handling-related injury.
Reviews in Fish Biology and Fisheries,
21, pp.43-49.
Link to the Paper
Abstract
Fish are coated with an external layer of protective mucus. This layer serves as the primary barrier against infection or injury, reduces friction, and plays a role in ionic and osmotic regulation. However, the mucus layer is easily disturbed when fish are netted, handled, transported, stressed, or subjected to adverse water conditions. Water additives containing polyvinylpyrrolidone (PVP) or proprietary polymers have been used to prevent the deleterious effects of mucus layer disturbances in the commercial tropical fish industry, aquaculture, and for other fisheries management purposes. This paper reviews research on the effectiveness of water conditioners, and examines the contents and uses of a wide variety of commercially available water conditioners. Water conditioners containing polymers may reduce external damage to fish held in containers during scientific experimentation, including surgical implantation of electronic tags. However, there is a need to empirically test the effectiveness of water conditioners at preventing damage to and promoting healing of the mucus layer. A research agenda is provided to advance the science related to the use of water conditions to improve the condition of fish during handling and tagging.
One potential drawback to water additives that contain Aloe vera extract or CMC is the addition of organic waste load that can reduce the water quality and oxygen levels in a closed system. This may not be an issue, depending on the density of fish, length of time fish are held, and oxygen content of the water. However, the effects of these substances on gill tissue are unclear. Taiwo et al. (2005) tested the survival and behavior of tilapia (Oreochromis niloticus) exposed to different concentrations of aqueous extract of A. vera for up to 96 h. One hundred percent of tilapia exposed to 50 ppm A. vera died within the duration of the experiment. Fish used in this experiment exhibited
severe depigmentation and destruction of organs (including gills). The evidence of the toxic effects of A. vera on fish solidifies the need to empirically test water conditioners, and their chemical components, for potential negative effects on fish.
While I do not think the amount of Aloe Vera in Stress Coat will come close to killing fish fish, I am not sure that it has no effect on their gills or that it does not do any harm in other ways.