I have a 55 gal planted tank w/ a 4- T5 tube tek-light fixture thats about 250 watts.sat.night my fiance calls me at work to tell me that the lights fell into the tank
So Im thinkin evrythings dead the tanks ruined,the lights are ruined,$400.00 down the tube.Im about ready to puke there for a minute.She also said she turned of the lghts at the breaker.So I finally get home,I check all the fish,thier good evryones alive,check the tank,no problems there either,so now I check the lights after drying them off as well as possible,They work
no sparks no nothing dangerous,they just work.after talking to my fiance she told me that she heard a big bang,went down stairs and saw the lights about half in the tank and still lit,UNDER WATER.so after all this I figured out that the aircraft cable that comes with the lights just snapped on the one end for no good reason.So in short if you happen to have aircraft cable holding up your lights make sure its stronger the the manufactures standard wire. 
no sparks no nothing dangerous,they just work.after talking to my fiance she told me that she heard a big bang,went down stairs and saw the lights about half in the tank and still lit,UNDER WATER.so after all this I figured out that the aircraft cable that comes with the lights just snapped on the one end for no good reason.So in short if you happen to have aircraft cable holding up your lights make sure its stronger the the manufactures standard wire. 