if the nemo is larger then your black and white then i woul dhave to say get it out, becuase when it gets established in your tank he will become the agressor and kill your black and white, but it is possable to get them together but you should have added the smaller to the larger, black and white will mate with orange and whites, they are the same clown, just slightly diffrent and from diffrent areas, but if you want them together find a way to get that black and white out of the tank and keep him in a diffrent tank for awhile and then replace when the nemo has become established and then it should work, but also they are going to fight for a few days no matter what you do but if the smaller one is the agressor when the larger fights back he IS going to kill it where the other way around the female would let it live after it showed him who is boss, but the larger will turn on the smaller and the smaller is NOT going to give up its teritory enless it dies, clowns will protect there domain at any costs and that is why its hard to get them together untill you understand the way they think
