Why? How many do you need? Are you going with a shrimp only tank? Are you trying to take care of a specific problem? You could keep a bunch in a 105 but exactly how many depends on your feeding regemine. In my opinion I would stop at what you have now.
I wouldn't put more than 30 or 40 in there. If you put in more than what you have now you'll need to feed then directly or who knows what they will eat when they get hungry.
