[greenbean36191]

Mine isn't really controlled by anything other than ambient air temp and a heater, but it goes from 78-83 in winter to 80-86 in the summer. Obviously since I'm not really controlling it the change is very gradual with the seasons and there are no real plateaus. I've never seen any noticeable changes from when it was constantly ~80 year round.

As far as the temp changes and spawning, seasonal changes are well documented to be important for priming a lot of animals for spawning. Basically they only start producing gametes or even gonads once the water reaches a certain threshold. After that, shorter term cues take over to actually trigger the spawning. There's also been a lot written on the importance of seasonal acclimatization and shorter term variation on coral resistance to heat stress.

The spawning you saw was most likely just a common stress response rather than an indication of health. Probably the most common way to artificially induce spawning in aquaculture is by dramatically changing the temp of the water (by more than the normal variation they would experience). A lot of animals actually spawn as a stress response.