Combine the shrimp and fish with the garlic, 1/4 teaspoon salt, and a pinch of pepper, set aside.
In a medium pot, heat avocado oil over medium heat then add the onions and bell pepper and cook, stirring occasionally until soft. Add in the tomatoes and paprika and cook, stirring occasionally until reduced slightly, about 5 minutes.
Add the coconut milk and stock and bring to a rapid boil. Add the shrimp and fish, making sure it is all covered, then cover the pot and turn off the heat. Let sit for 15 minutes - the fish will be cooked through by the residual heat.
Stir in lime juice, garnish with more cilantro and harissa, if using.