you can add pods to your system anytime. if your natural supply has been depleted, you can periodically add them. use only pods that are natural form the reef area you are mimicing. add the pods to your refugium if you have one. otherwise you could put a hangon box with a small pump, several pieces of live rock and add to the as a intermal refuge. they will then disperse into the main tank. naturally there are many ways to do this. point is to let them establish and disperse into the main over time, unless you have animals that are knocking them out quickly, then you may want to add directly to the main in a protected area. good luck keep us posted.