I wouldn't add anything else to your tank until you have your current problem under control. Eight hours of light is adequate and it won't hurt the coral to be without light for a couple of days. Now that you've added a coral you need to be concerned with both Nitrate and Phosphate levels. Maximum acceptable levels of both are 0 for long term health.
Welcome to the world of reef tanks. If you haven't been using DI water in the past, you now need to start doing so for both make up and top off water. You should most likely start planning to get your own RO/DI filter. With the PC lighting that you indicate, you can keep corals requiring low to moderate light. I suggest that you start familiarizing yourself with the requirements for specific corals. You should also learn as much as you can about how to properly maintain a reef tank.
You are getting into expensive territory. Based on your initial post, you don't have enough live rock, you don't have a good protein skimmer, you don't have a RO/DI unit, You do have a filter (which isn't effective and is adding nitrate to your system), you haven't mentioned what your parameters, and you have just added a coral (from your description it's probably a LPS) into an environment that it has little or no real chance for long term survival.
I don't mean to be harsh but you are moving too quickly and are setting yourself up for failure. If you intend to continue in this hobby and have success you need to slow down and regroup. See if you can find a friend who has a reef tank to keep your coral for you until you have your current problem solved. Do what BoomerD said. You may want to consider completely starting over with 40 lbs of live rock, a good skimmer, and DI water. In the long run, it may be easier than correcting your current problems. You will also need good test kits for PH, Ammonia, Nitrate and Phosphate as a minimum. I would suggest Salifert for nitrate and phosphate.
