IMO get rid of the hang on filter you have on the back for starters they are nitrate factories and will lead to alot of algea in the future the next money you will want to be spending is on a good quality protein skimmer they are worth their weight in gold for removing dissolved organic waste, as the rock cycles you will have more waste being introduced to the tank, the white stuff you are seeing is the die off of micro organisms sponges and other things that used to live on the rock sad but true your ammonia will go through the roof as your rock cycles please for the sake of anything else you are going to put in there, wait until your tank has fully cycled and you have a good quality protein skimmer also make sure during this period you have your power head facing your rock to blow off any waste that it is producing. the biggest thing here is take your time, a stable marine tank relies on bacteria to break down ammonia and nitrites, let your tank stabilize and populate its bacterial filter then and only then you can start to add fish nitrates are okay but nitrites and ammonia will kill your fish and corals next is lighting you should read up on zooxenthele and the way corals produce it through photosynthesis. enjoy your new found hobby and remember nothing good happen right away in marine
