UV rays

[Amstar]

ever heard that if one of your metal halide bulbs is cracked/or malfunctioning it can give off to much uv light and harm your corals?

[REDPYRO]

i would assume if it was cracked it wouldnt function

[verper]

Yes, that is true.  Double ended metal halide bulbs must have a glass cover over the bottom of the reflector because they do not have the bulb within a bulb setup like a single ended MH bulb.  The glass decreases the amount of uv radiation that would go into the water.  Being cracked may not be enough to harm your corals, but missing pieces of glass on the outside envelop would.