In a 2 quart sauce pan, heat the oil over medium and sweat the garlic and the crushed red pepper for 2 minutes. Add the calamari, salt and parsley and continue cooking over medium heat until any excess liquid from the calamari has evaporated, about 6-8 minutes. Reduce the heat to low. Add the canned tomatoes, including the juice, and cook for 10 minutes, stirring occasionally.
Increase the heat to medium-high. Add the shrimp stock and bring to a simmer. Add the Swiss chard and the spinach, reduce the heat to low. Cover and continue cooking for 30-45 minutes, stirring occasionally. Do not let all the stock evaporate. There should be about ½ cup of liquid left.