Samuel Warren wrote:
Update: The Opaline Gourami died today. I Just got him 2 days ago. I am
going back for a refund (15day policy). I thought that he was acting sort
of wimpy yesterday, perhaps this was why the Rainbow Shark was protecting
him.

I was changing out 6 gallons from my 40 gallon tank. I treated the 6
gallons with Stress-Coat and let it set for about 15 min before I put it in.
I went to supper, When I came back he was drifting in the tank with
occasional spurts of swimming. He then began to roll over and became lodged
along side my drift wood. The Clown Loaches started to "inspect" him, and
he made little attempt to flee them. It was then I rescued him from the
tank into a small tupperware bowl, where he left the world in peace about 15
minutes later. All other fish seem to be their spunky self. I tested the
Ammonia at 0.0 and the Nitrite at 0.5. So after reading my story from
yesterday, maybe my Gold Gourami knew something was wrong with him, or had
terrorized the poor Opaline to death. What do you guys think it was?

A stress death is sometimes black or dark colored due to heart attack
according to my local fish store.