I will keep you all posted throughout the next few months on how it's doing in the tank and what it ends up being.
.... He also suggested to only feed it 1 good heavy meal a week and two smaller meals. He said that he fed the shark a krill or dead fish every day but got the good meal once a week. I'm definately not going back to this LFS again after this issue.
Forgot to say something about this part. You're right for not listening to the feeding advice. Young sharks like this do best with small meals daily... maybe 6 days a week with one fasting day. 1 pc of krill doesn't count as a meal for them.