Might wanna re-think that galaxia. They are described as corals that "do not foten survive well in the aquarium". Thats a quote form Eric Borneman, a renowned coral expert. I got that from his book, "Aquarium Corals, Selection, Husbandry, and Natural History". Here's another write-up that cautions about the galaxia's nasty sweeper tentacles that will damage nearby residents. And you only have a 24g tank. Looks like a bad thing about to happen if you get it. Sorry.
Oh. My manners!!! Welcome to AA!