I put a yellow watchman in my 3 gallon pico, and it is still very timid 4 months in. They are very heaty and don't mind fluctuations in water quality, which will be your biggest problem. I top off w/ RO every 2 days, pull 1 16 ounce cup out every 7 days, and replace with water from my main tank which gets 10-15 day water changes. good luck!!! It is a lot of work for a tiny little tank.