I have been accused of having an overstocked 20 gallon (see list below) and due to the activity level of the danios I have been accused of improperly housing them in a 10 gallon. From what I can tell the fish don't mind
It is possible they are in there saying "lemme outta here!!!!! I am cramped" unfortunately I have no way of gaging that. No one is being aggressive towards anyone other than my Gourami who is a bit of a brat. My understanding is that this is normal for a gourami so I have never been concerned. Although he is a brat he does not harass and harass and harass. He is just brattish about his food, and everyone elses.
100 gallon is not even fully stocked yet so I can't say if it will be over stocked in the long run. I am having to rethink the Burmese loaches. At 16 bucks per fish I just don't think so LOL.