Cyanide collection isn't totally gone, but it's nowhere near the problems it used to be. Properly trained collectors actually catch MORE fish without using it, and without the cost and danger of working with cyanide, and lions typically aren't caught with cyanide, but I digress.
What does the lion look like? Check its eyes, its fins, its body for spots or lesions. Is the fish breathing heavily ("gilling")? What are your tank parameters?
"Facing the wrong way and not moving" doesn't give us much to go on.
In the meantime, I'd add some Vitamin C and B6 (Thiamine) or a B complex to the tank. I'm not a fan of Selcon because it mostly washes off of the food unless you feed it to live food.