First of all, you'll want to keep the galaxia somewhat isolated from the rest of your corals. I keep mine on a little rock island in the middle of my tank. It'll tend to throw out sweepers that can get pretty large, and apparently these can kill off other corals very easily.
They're pretty slow growers; as you can see in the pics below, in the span of 2 years mine has just now managed to encrust the rock it came on completely.
For me the galaxia has been a pretty hardy coral (though I know this may be just dumb luck). My tank had a pretty bad ozone overdose and then more recently had to be completely rebuilt because of a leak in the tank. Through it all the galaxia has come through completely unscathed.
Every once in a while I will target feed mine some cyclopeeze with a baster.
As I said before, mine is the in the middle of the tank near the bottom (24" tall tank). I run 2 x 250w 20k radiums and 2 x 54w blue+ T5s. Flow comes from two Tunze 6101s.
I've observed that it seems to do best in swift flow, but not being directly blasted. You'll know if there's too much flow if it closes up.
My galaxia in December 2005:
My galaxia on January 2008:
Overall I have always liked this coral. It provides a subtle movement to the tank -- like watching grass on a field ripple in the wind.
Tyler