I am new to the saltwater hobby. I have had my tank set up and cycling with live rock and live sand for a little over three weeks now and i do not have any algae growth at all.. Is this normal? Is this ok? Do i need algae growth in order to purchase a clean up crew or can i supplement them with other foods? If i need algae in the aquarium what do i do to promote its growth? Thanks for all the help in advance.