I'm guessing they are under 3", and in that case, keep them by themselves. I would suggest until they get over the 3" mark to keep them in a barebottom tank with only the EB's in it. They are ver sensitve to water quality, very easily picked on, and very messy. If you MUST have something, some kind of juvie liver bearer(s) would work. Keep in mind though, whatever you add is also going to add waste to the water.
Congrats on picking up a great fish though. They have a great personality, and when they get larger are even more beautiful than their cute juvie forms. You have yourself a very rewarding fish.
If they are expensive or hard to find in your area (as they are in most areas) I would take extra steps to protect them. A UV light is a very worth while investment when keeping a species known to be sensitive toward parasitic illnesses.
I found my Dominant Blue Dempseys to be as active/aggressive as standard Dempseys, although slower growing. Firemouthes are slow growers as well and Iâ€™ve had good luck growing them out side by sideâ€¦
If I were in your shoes and had a 180 gal as the long term home for themâ€¦ I would grow the 3 out with some live bearers until they are 4~5â€
I have one juvie EBJD, in a 40G tank, with a couple cory cats and a small shool of diamond head tetras. The activity of the tetras seems to help with his natural nervousness, and the cory cats are his favorite dithers, he is always chasing them. I had half expected the tetras to start disappearing, but none have yet.