In addition to all the great advice which is all correct, coralline will not grow if you have hi phosphates... (keep that in mind) Also, if you do decide to seed your tank (which I recommend) make sure the rest of your rocks are clean. You can simply pulled them out one by one, depending on how many you have and simply brush them off with a tooth brush. Coralline will not grow on slimy surfaces surfaces, so I've heard. Parameters: VERY IMPORTANT!!! I recommend B-Ionic. It comes in two parts and it's seriously the best stuff out there recommended by marine aquarist all over! Stay away from the "purple up" stuff.. I heard that you do get coralline with it but it's not the same. I heard a lot of negative things about it.. Good luck bro, I'm on the same track as you and I"m beginning to see results doing some of the things I mentioned. keep your calcium high 450-500 ppm... Do frequent parameter checks because the alkalinity kinda offsets the PH.