Half Dead Fantail

[Jazzzz]

So what can I do, the poor thing has been in a crowded non filtered tank of goldfish (not mine) and is lying on its side, made a move for the food.

So far I have removed and isolated him in a clean tank with fresh water.

Anything else to do

Thanks

 

[WILDER]

How many gallons was the tank.
How amny fish and which type.

Does he look bloated.
Does he look darker in colour or pale.
Is he actling listless and lethagic.
What does it look like when he goes to the toilet.
Any red streaking on his body or fins.
Any sores on his body.