Was the rock cured or uncured? Did your tank already go through its cycle (ammonia and nitrite spike)? Just curious to where you are in the cycle. If your parameters have already peaked out and are back to zero (ammonia and nitrite), then I would slowly increase your photoperiod. Start out with a couple of hours and gradually increase the time on lighting. The photoperiod when cycling a tank can be debated. Some feel that you want the lights on to preserve the life on the rock, but I feel they should be off until the cycle is complete. Algae love a couple of things....nutrients and light. Algae is, unfortunately, part of the early stages of tank life. When the tank is cycling - there is a bunch of nutrients available.....add some nice strong lighting, and you will have algae in no time! I like to think by having the lights off, that is minimized. You will be amazed at what life remains on the rock after being without light. You have a good amount of rock in there - that's great! What are your plans for the tank? Let us know how it does...