Evening Gentlemen
I have a few pips of info that may be of some use (at least from an English point of view

)
1. You have a claim based around the demise of your beloved fish, so at the very least you MUST have the value of the fish (fully grown) refunded to you (likened to if someone broke your ming dynasty vase. You don't get the original value of 3 yen, you get $3 million(current market value))
2. Money back, in full, from the pet sitter, instantly!! Amounts down to false advertising and failure to deliver the advertised service.
3. Emotional damage also comes into it. Someone earlier in the thread likened it to someone killing you dog. I agree on the same principle. Some one has come into your home, and bumped off several of your pets, if your so willing, you could claim from emotional retribution.
4.Investment (probably wont get away with emotion claim and investment claim but its all down to circumstance) if you've spent $15,000 on feeding, keeping and rehousing a show class tire track ready for the up and coming shows, then surely, they have wasted your money. Someone should pay for this wasted investment.
5.Loss of earnings. Again, on the same track (excuse the pun

) if you did ever want to show this, very impressive eel, with the possibility of winning money, then you have grounds to claim for this too.
Price tag for an eel is irrelevant, as many people have said on this board before, its all down to the value of the fish to YOU. I'd wade in with an exorbitant amount, including the cost of the tank (now useless without fish), food, fish and maintenance. Pile on top of this, the emotional of financial damage caused by the neglect of a professional pet sitter, and you can pretty much demand the price you want them to pay.
Best of luck with it all. (Any problems, please feel free to send me a PM, i know a few legal bods over in blighty)
Best of luck
Craggy
(very sorry for your loss)