i have bamboo shrimp, unlike other shrimp, these have fans instead of arms, they are borwn in color and ahve a white strip going down the back, in the wild they are found in red tones. They get about 3 inches. They ussually move around the tank to fins a good current and stand in front of the current and filterfeed. Incase anyone is confused on what filterfeeding is, its when they filter the water for algea or other organism. I drop 3 small algea wafers in ever couple of days, it desolves in the water and the current spread it out, at this time the bamboo shrimp filterfeed into their mouth. There very cool to look at when they feed. and ur 20gl is enough room, i have 1 in my 10g, had 2 but one died :-(. Make sure u clean ur gravel tho, to much waste can make the bamboo sick, and they tend to filter feed on the decor and gravel, so just maintain the tank clean and they'll be fine
