Originally Posted by Wasabi
Yes I took my time acclimating him over 45 mins. Other than the high filter flow and possibly the salt water aquarium, I did notice when I first put him in, he would see his reflection in the glass of the aquarium for the first day, now he totally ignores it. If that is the problem, I have no idea how to rectify that problem, bar keeping a blanket over the tank in order to keep him in constant darkness lol.
In terms of the reflection problem, putting a non-shiny blank piece of paper around his tank might fix that. My rescue was flaring at his reflection in the filter base behind the glass. All I had to do was shove a bit of paper there and it worked.
Gyarados (pictured) is very sensitive to reflective surfaces and will flare and stress out all the time if he sees even the closest reflective surface outside of his tank. So I just remove that or put it behind something non-reflective.