How does the minirank system work exactly?

I recently acquired the sand box participant mini-rank and I'm curious as to how you get it. Do you get a rank after you post in the forum a certain amount of times or something? And ranks like potomus, how do you get them?

 

Participant ranks are given automatically if you post often enough in whatever section.

Potamus, Archer, Homosex and all the random such miniranks are awarded for competitions and the like

 

Oh i see, thanks