....is it hard to move an established tank??? like say i move cross country how would that work?
To move a tank of that size, 125 gallons, it could be a real challenge. Not that you COULDN'T do it but you have to think, you need to have all of your livestock placed into something with enough room and then you have to maintain the temperature at a reasonable level and probably good to have some water flow if it is a long trip.
You will probably have some sort of die off from something, especially if you have corals and then you have to keep your live rock at LEAST wet but preferably submerged and then, again, you will have some die off.

Sorry if it's discouraging but you need to know what you are getting into and have the patience and willingness to take your time and do it right.