Brussel sprouts, cabbage, broccoli and other plants in the Brassicaceae all tend to have moderate concentrations of oxalates and high goitrogens and should not be used as staples, but are fine if fed occaisionally. This site: http://www.beautifuldragons.503xtreme.com/Nutrition.html has some good nutrition info, but the feeding recommendations are geared towards lizards. Here's a page that has some good tortoise diet recommendations: http://www.maturtlerescue.org/tortoise_nutrition.htm

-Alice