Do you have a
protein skimmer? If not, you should get the best one you can afford. If you can find someone to drill your tank, you should get that done as well and add a sump. Use the RO water and forget you ever had the tank set up to begin with. You will be starting the cycle over. Make sure you get a
nitrate test kit to start with. Once your live rock is doing the job and you have good skimmer, your nitrates will be low enough to add a few things. Don't rush it. If you can be patient at the beginning your chances of success will be greatly increased and you'll enjoy your tank a lot more. I would keep the sand, but that's a matter of opinion. Your tap water prolly got you off on the wrong foot to start with. Don't worry about that now though, just use the RO and be glad you figured it out before you added anything. Just don't be in a hurry. If you are going to add corals, use the next month to get acquainted with alk and calcium and how they interrelate. You'll want a salifert test kit to test your alk levels. If you can keep your nitrates down and your alk and calcium levels optimal you'll GROW corals instead of just keep them. That's my two cents.