what corals can touch other corals without problems? i have found brain corals and modern corals can do it and it is neat to have them side by side. any other combos?
I don't know if there's any hard and fast rules one could go by here. While two corals might not declare outright war on each other, there is always competition for space, light, current, etc. I'm surprised you've had that experience because I've noticed that Faviid corals will send out surprisingly long sweeper tentacles to sting nearby corals.
We have a neat example of a mixed Montipora digitata and Zoanthus sp. rock where the "winner" of the war changes depending on what side of the rock you're looking at. For whatever reason on one side of the rock the zoanthids dominate and grow right over Monti skeleton that they've stung and killed--meanwhile the Monti grows over entire zoanthid polyps on the other side of the rock.
My open brains can touch each other with no problems (short sweepers). Matt's right though, my favia's tentacles are pretty long! Not as long as galaxeas, though. Euphyllias are alright but only with each other. My zoas can usually grow side by side.
I try not to keep any of them close to different corals unless they're leathers. My leathers touch each other with no adverse effects. Oh, and mushrooms too.
This post was pretty incoherent and I need to get to bed.