Full moon is an external stimuli. The main trigger for most marine spawnings are either lunar cycle ( I've read alternatively that the tide - which is driven by gravity - and the actual light, which is why they usually happen on clear nights are usually, is the main one but I'll see if I can find anything more substantial ), temperature changes or nutrient fluxes ( which are due to one of the previous two as the plankton, which forms the base of the nutrient chain, are light and temperature dependent ). Stressors such as those that lead to polyp ejection are not cyclical events. They are adverse events for which many corals have developed this adaptation. So while I was not saying that our tanks are completely out of tune with the external ( external as in nature, not as in what we do to it ), the more immediate and probably bigger effect is from what we do to the tank. For instance, most people probably do not have very precise temperature control. Even with a chiller and heater, its probably that your tank fluctuates a degree or two with the seasons. Thats what happens in the tropics - only a couple of degrees change through the seasons - while in other regiions it can be greater. Salinity is another big one. In coastal regions, such as where many reefs are found, seasonal rains ( and the runoff caused by them ) cause slight salinity fluctuations, which in turn cause nutrient fluctuations, and so forth.