reef tank, effects of upgrading from 100w t5 to 300w MH?

You will definitely want to move some of those corals to the bottom. Ricordea, Star polyps, and even Xenia do better in low-moderate lighting and will likely go into photoshock and die if you switch the lights suddenly to bright. I would also recommend cutting back your photoperiod when you first install the bulbs, and slowly lengthen it again over a week or two. Your hyndophora is likely turning brown because it is not receiving enough light, but it will still go into photoshock--along with the others--if the lighting is switched suddenly. Make the change as gradual as you possibly can.

Lots of humans say that steel halides are the pleasant lighting fixtures to be had as they're more often than not the nearest factor to the exact solar. Metal halides provide off a favored shimmer outcome as good. Under a steel halide, you'll be able to preserve plenty of types of corals/clams, relying at the wattage. T5 lighting fixtures is practically the following pleasant factor. If you are retaining a reef tank then I feel a T5 lighting fixtures might suffice, considering that steel halides may also be pricey. Metal halides can purpose a lift in temperature as they may be able to be relatively warmer than the T5's. I feel it is all a question of private alternative, whether or not you opt for that shimmery appear of the steel halides as opposed to the average appear of the T5 lighting fixtures.

i changed to haylide lighting and mine where fine but just becareful if you have a happy tank i wouldnt change it unless you have to as your corals have set to your lighting