Just be sure it's safely attached and won't fall into the water. Be sure you have a properly grounded fixture and plug into a GFCI protected circuit. Home Depot has portable plug-in ones. Even without lights, you are already creating a refuge for copepods and amphipods just with the live rock. The sand is a good place for worms and such. Keep crabs and fish out of there, you can add a little flake food now and then if the tank return water doesn't flow directly into it. Otherwise, they will live on the bits that come in from the overflow.