Baby whale fish

[Al514]

How can I know when baby whale fish is sick? I bought this baby Whale fish and my wife is worried about the color. The seller told me the fish is healthy. I have no experience .. I like the fish . I am looking for more information that can help us.
Thank you.

 

[Delapool]

The search function might also help. I haven't seen a thread on these for a bit but do remember threads.