Hello. I have a 37gal freshwater tank that I really like but I purchased another tank over the weekend that I am making a saltwater tank. It is just a 6gal NanoCube tank. I have bought the live sand and 7 lbs of live rock. With the NanoCube (very impressed with it by the way) there is a regular light for the saltwater and a new LED light for at night. My question is how much do I want to light the tank. With my freshwater tank I have it on a timer to go on and off a couple times a day and they get about a total of 12 hours light. Also, with the live rock that I bought from the local place, a great sea urchin was hiding in one and has come out since I put the salt water in. Does that guy need food or does he just feed off of any organisms on the rock? Thank you for your help!