I have had my six Zebra Danios from the start of my tank, four weeks ago. One of them is crazy aggressive(he has been since the start of the tank, I got him from petco) I decided to finally quarantine him in a fishbowl, after I saw all my other fish extremely stressed. He’ll be there until I can figure out what to do with him. Please help! I think he is a male( are those silver?) and the others are female(gold?).