Clean the fish by removing all the fins, tails, and scales from the body and head. Rinse well and set aside.
In a pot combine radish slices, sea kelp and water and bring to boil. Simmer for 3-5 minute until radishes are somewhat tender. Remove the sea kelp.
Add the fish and the kimchi seasoning paste to the pot. Smear the Korean soybean paste to incorporate to the broth. Boil the stew over medium heat for 4-5 minutes or until fishes are cooked and the radishes are tender, spooning up the broth over the fish occasionally.
Taste the broth and season with the Korean soy sauce for soup according to your taste.
Add the slices chili at last and cook for 1 more minute. Remove the pot from the heat and add the green onion and the arugula at last. Serve hot with rice.