Chromide on rampage, beat up molly, help ASAP!

[omplmpa3]

Well it has finally happened, my sweet, little, inquisitive red chromide has become a savage bully overnight. I have a 40B brackish community tank. I just went down to feed them and I found the very pregnant black molly in the sand with the chromide sadistically nipping at her fins. At the moment they are both in plastic bags floating in the tank. I think the molly will be okay with some treatment. My dilemma is where to treat her. I have a 15 gallon that I've been breeding snails in. The water quality is great, could I remove the snails, add a small amount of instant ocean along with some filter media from one of my brackish tanks and let her recovery in there? Or should I treat her in the 40 and put the chromide in the 15? The other residents of the 40 are mellow and I don't think they would bother her. But the chromide needs to be removed, he was already looking for another victim.I have an empty 10 I could set up if necessary. But it would probably be best to utilize a tank that is already established. Any advice would be great.

[LilGreenPuffer]

Adding salt to the 15 might wreck the biofilter anyway. How much salt is she used to? Raising the SG more than .002 will crash it. Mollies can take a big SG swing, though, so with a bit of acclimation, .002 would probably be fine.