Hi Caper,
The spots are called 'Egg spots'. I believe most Zebras, of any colour, have them and its more dominant in male fish. During spawning the female lays eggs then picks them up in her mouth. She trys to pick up the egg spots on the male and gets milt in her mouth instead....thus fertilising the eggs.
They can be aggresive enough to hold their own in a Malawi species tank but not bullyish, at least mines not.
Hi smidey
All the stuff I've read about NLS says that it enhances the colour of fish and nothing has been mentioned about spirulina causing any grief. I'll keep this thread updated with pics......we'll soon know one way or the other.