Sweet tank. Looks great.
About your rocks, they look pretty cool. Random rocks can sometimes leach into the water column and raise your ph pretty dramatically. If you like the look, you can always test it with a drop of strong acid. If it starts bubbling, then you have a base which will leach. By the way, vinegar is too weak. Use something like muriatic acid (HCl) which you can get at home depot or lowes or any swimming pool supply store.