Welcome !! It is crazy exciting setting up a new tank, especially a large one! I also have a 125. Just make sure to take your time and plan out what you'd like to display in the tank and watch grow. And remember try not to let it stress you out and just have fun! :) If you take a look at that set up guide Kschweer posted it will give you a lot of info on utilizing on the equipment you already have. Good luck!