As far as I have tested karamthulhu won't go in fishbowls, fishbowls+bag of salt, fishbowls with seaweed, fishbowls with fish, fishbowls with fed fish, all other varients of the above with fishfood, and all of the above with fishing bait. Any other ideas? edit: On the 2nd floor south side of the petshop there are boxes of fish food and cylindrical tanks maybe those contain it?