Stress Coat is one of the most popular dechlorinators on the market, however, there is a lot of confusion surrounding it. I’m writing this up so I can help my fellow fish keepers when choosing dechlorinators for their tank(s).
First of all, Stress Coat is a proprietary formula, which makes it impossible to know what the active ingredient is for sure. Most third-party sources say that it is sodium thiosulfate (Na2S2O3).
Sodium thiosulfate is ineffective at reducing chloramine unless used in dosages considered dangerous for fish. So, assuming that Sodium thiosulfate is indeed the active ingredient of Stress Coat, then we know that stress coat is a poor choice for aquarists who have chloramine in their tap source.
https://www.google.com/2007/04/aquarium-water-conditioners.html#stress_coat (The link isn't working) - this website says:
Purigen or other filter resins.
I did try to get in contact with MARS Fishcare to confirm that they used sodium thiosulfate in their products. This was before I knew that Stress Coat’s ingredients were confidential. Here is the response I received:
https://www.apifishcare.com/pdf/Stress_Coat_Cortisol_study_8.1.08-1.pdf
Thank you,
Taylor K.
Consumer Relations Technician
MARS fishcare
T+ 1.800.847.0659
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The link shows a study that tests the effectiveness of Stress Coat as a cortisol (slime coat) replacement.
https://www.apifishcare.com/pdf/Stress_Coat_Cortisol_study_8.1.08-1.pdf
However, an independent study by The University of Georgia found this:
It should be noted that testing has shown that Stress Coat is only effective in direct application whereby the "blob" of slime/aloe lands directly on the fish.
This seems very unlikely, as most aquarists simply pre-treat their water, which lets the Aloe Vera disperse in the water, thus, deeming it relatively useless for fish. So, to ensure that Stress Coat is being used as intended, one must:
-Be sure that there is little/no chloramine in their water source
-Physically tip the Stress Coat onto their fish
-Not use resins (including Purigen) in their filter
All of these seem improbable, so I highly encourage aquarists to use an alternative product.