Rainbow shark question

No.
 
no,its way too small of a tank(rainbow sharks can get 6 inches)and the tiger barbs would pick at him constantly.
 
Nope. I have a 4 inch Rainbow Shark 50G tank and personally I think that is the perfect size tank for this species. Any smaller and aggression becomes an issue because basically they are uncomfortable/unhappy. He was in my 20G when he was much smaller and he was a just plain menace. I don't think there is any type of shark you could put into a 15G (correct me if I'm wrong).
 
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