Interesting article.
http://joshday.com/mandaringoby.htm
Due to the heat on this topic, please forgive the following disclaimer. However, if you've ever had a passing interest in mandarins and possibly keeping one in a nano tank, you've no doubt seen the blatant hostility from all the nay-sayers out there. I've done a lot of reading about mandarin dragonets, and I've come to the conclusion it is possible to house them in a nano tank as long as they are given the right conditions.