i'm setting up a 10 gal tank, just gotta let is cycle. heres a pic of it so far, and im thinking about taking some water out of my 125 and swapping into this tank
i dont see how that wouldnt work, if the tank is cycled and its the sand from it, why not? but if you do, you might want to wait a few days before adding fish, could get a spike from moving everything around.