Just bought 1 Tiger Oscar + 1 Tiger Barb. The Oscar is about 3 inches long right now. The Barb is about 1 1/2 inches long. When my Oscar gets bigger, will I have to worry about him eating my Barb? Should I return the Barb and purchase another Oscar? The Oscar has been territorial since being placed in the tank. And do these Oscars really reach lengths of 10 to 12 inches?