IMO, I would stick to aragonite. Atleast you know it is a proven safe substrate that has a good buffering capacity and releases trace minerals into the water. What happens if their is a problem with the sand or limestone substrate you want to use? Then there is a major job or removing the substrate not to mention the live rock that has to be removed and the inhabitants in the tank. I just would be a little hesitant in using a media from Home Depot or Lowe's as substrate for my expensive hobby!
Good luck with your decision, maybe limestone will work, just want piece of mind found in aragonite. _________ 125gal.w/Mag9.5 return(dual megaflow)>Mag7 pump Aqua Cev180skimmer.Wave2k Hamilton Reefstar(2)250watthqi(mh)pend.a Yellow, Naso Tang Red Lip Blenny Percula Clown Demoiselles Niger Trigger F. Wrasses Ceriantharia Orn.Shrimp and Stars Hermits Queen Conch asst. snails> Stars Zoos shrooms Montipora Brains Gorgonians Favia Turbinaria(large+small polyp) Acropora Xenia Tridacna (CroceaMaximaSquamosa) Leathers <35+75gal.reef tank as well> 
"IF THE PHONE DOESN'T RING...IT'S ME"  jb  | 
yardright 
)
