Two weeks ago I established a new tank (20 gallons) and first added 3 tiger barbs and 1 opaline gourami, just today, I added a loach as well as a pearl gourami. The problem is that the opaline is very aggressive towards the pearl and is trying to grab a hold of its fins and pull. I can tell because normally the opaline has light grey/pale blue scales and when I add the pearl gourami, his scales changed to a dark blue. What should I do now??? Im afraid the pearl one will die from stress, he's trying to stay in a corner and get adjusted, but the opaline keeps biting him.