Although this is an older thread, I wanted to report my own experience with H. magnifica. I held one for about 13 years under T-5s, during which time it split once. Although most find it a difficult species, mine was always happy, healthy and, above all stationary. It was close under the lights in good laminar flow, generally with clown fish.
When it split, it happend rather suddenly, over less than a week and I actually thought it was dying. It spent most of this time partially collapsed and then suddenly recovered and was two. I think it was about 8 years with me when this happened.
To be honest, I never found it sensitive to water quality in the sense of occaisional nutrient spikes. Good light, occaisional feeding and free moving current seemed to be the key criteria.
her name was Monika and later Monika II. I parted with them about 5 years ago, now.
Just to share something positive about these often puzzling animals.
