Gah! Another mini catastrophe!

So in my journey down the road of reefkeeping, I encountered another *bump* in the road so to speak, last night after spending the day out with the fam.  Got home, went in, looked at the tank and noticed something shiny sitting on top of some rock.  Looked closer and determined it was small hunks of glass /DesktopModules/ActiveForums/themes/_default/emoticons/sad.gif  Hmph, I wondered where the hell that came from?!  Broken glass in relation to a large tank full of water is NEVER good......my first thought was OMG, the tank is broken somewhere, somehow.  Of course, it wasn't that   I looked up to see tiny shards of glass clinging to my halide though........  somehow, the glass over the halide fixture broke, into, oh, about 5,000 pieces or so /DesktopModules/ActiveForums/themes/_default/emoticons/crying.gif/DesktopModules/ActiveForums/themes/_default/emoticons/crying.gif/DesktopModules/ActiveForums/themes/_default/emoticons/crying.gif  Looking closer, I could see my large toadstool, acting like a basket, was holding the majority of the glass pieces.  Its safety glass, so it broke into *chunks* vs. shards, so really, nothing has been injured, just a ton of glass was broke into my tank /DesktopModules/ActiveForums/themes/_default/emoticons/cry.gif
So that's my sad story.  I'm wondering, of course, how this happened, to avoid a repeat disaster.  A few days ago, the bulb in that fixture was flickering and going off for a bit, then coming back on.  So I took the fixture down, but an old spare bulb I had (not new), cleaned the glass etc. with a damp cloth, put it all back the way it was.  The only thing I can think of, is that one of the powerheads has been getting more and more crowded out/deflecting off the mammoth toadstool, and so has been making a tiny turbulence on the waters surface.  Its really not much.  The fixture sits about 8-9" above the water.  I'm thinking something, maybe a fish somehow swam near that powerhead and made a big splash of water onto the hot glass and it shattered?
Any thoughts?  Has this happened to anyone else?  I luckily have another identical fixture and was able to steal the glass from that so I can keep running the light........I've moved it up some and moved the powerhead.  I'm just worried its electrical or something.  I've never had a problem with the light until this happened.

 

Oh that's good to know that its probably not electrical! I'm paranoid now-going to go make sure its loose enough.....