I've just changed from 4 fluro tubes over my 40gal reef to a 150w MH light. Now the corals don't seem to be opening fully. Is this just temporary or don I need to do something. The lamp is for marine use and the bulb 6 months old.
You have to give corals a chance to adapt to higher lighting, they can actually be killed by too abrupt a change. Is it possible to lift your lighting fixture up so the intentity reaching the corals is less? That would be ideal; then over a couple of weeks you can slowly lower the light. If you can't do that, try cutting back the day length, and then each day increase it a little until you're up to a full day.
