I've had my chili coral for about a year now and mine does fine all on it's own. I haven't been feeding it, but my system is pretty mature.
It was a huge piece when I first bought it, around 8" colony (retracted) with maybe 24 fingers. When I got it home, I put it in my tank where I thought there was plenty of space. It expanded that night and Wow! it became 3x it's size. The extended fingers, polyps with white tentacle tips are so much more beautiful than the deflated stubby dark red stumps. Color brightens up to a lighter red too. I wish I could get it to stay like that in the daytime. In the morning, they fully retract within 15 minutes of the lights going on. After about a month of unsuccesful early morning feeding attempts, it started to stop expanding at night. Dark cyano started growing on it and it looked like it was starting to go down hill. I tried marine snow, phyto, even cyclops to stimulate a feeding response but it doesn't seem to react to any of that. I finally discovered online that stirring up detritus in the sandbed just after lights go out seems to stimulate expansion, so it must be a bacteriavore or filter feeding on the detritus. I started doing that a couple time before going to bed and it's been happily expanding at night ever since. I've fragged mine a couple times now and placed a couple pieces in my nano tank. It seems to be even happier in there. Probably more nutrients in the water and the detritus in that tank is a milky grey color. They haven't grown much since I got them, but they haven't declined either.
Now that I also have sun corals and have been feeding those at night, I might reattempt feeding the chili after expansion to see if it makes any difference. Anyone have any luck with that?