I'll third the not happy vote . Your tank is or will be way to small for it. What sort of fish do you have in there and how attached are you to them? I'm not trying to flame you or anything but, sooner or later it's going to start munching on them if it makes it.
I'd also guess that your tank is pretty new and they really don't like anything but a well established large sized tank that has really stable water chem ph,salinity, low nitrate levels etc. If possible I'd trade it in or give it back to the fish store.
Sorry, I know that this isn't what you wanted to hear and to answer your last question let it go where it wants.
hth and sorry
Chris