I agree I recently had a bad exp with tigers my vt angel fish lost 15% of his fins a lot for his size I got rid of them I also didn't know how nippy they are my brothers Betta lost 90% of his fins and nearly died because of it and due to opalines long ventral and anal fins they would have a snak on them
oops. sorry, i only read the top part of the post, and since the tank is only 125 liters I would say that that tank is unsuitable for a shark as they are territorial, and deserve a 4 foot tank, so are unsuitable for the OP's tank