I have had a rainbow almost two years in a 55g. (S)he has gone through three caves and one vertical hiding spot. Hardly any aggression except to the 1)blue rams which fought back, sometimes as a group effort. 2) Zebra loaches, but only when (s)he is swimming. It is odd because they often share a large stump cave 3) cherry barb. I had an adult in my group which got harrassed constantly. I had to moved the whole group earlier this week.
None of the aggression was very malicious in my case, but I hear that it can be. As far as hiding, mine is out most of the day gliding around the tank as the undisputed ruler :shark: