That is my bet... Since I wasn't trying to simulate anything, I have the aquarium lights on when it's convenient for me. The light goes on at 2 pm and off at 2 am... Throw in the natural light that comes in during the day before the aquarium light comes on and well, there you have it. I guess I am just amazed they are spawning in an open aquarium like this and a GSF and RBS. They look nothing alike!