my tank get smell after hour of mh light are ON why?

[khoivo1]

hi ,,,i have 2double ended175w mh light and 2actinic 96wlight
when i turn on mh light about an hour i can smell something coming out from the tanks but not sure what is it?? but the actinic light on is fine ,,no smell at all,,,i wonder if the mh light is too hot or something from burning,,, i have a acrylic tank with canopy and two fan ,,,any idea??
how far off from water and light?? does t5 does that too or just mh ?? thanks

[1F2FRFBF]

Can you describe the smell a little better? Is it like plastic burning, or is it electrical... ?

Your metal halide should be about 6 to 8 inches above the surface of the water, and the T5's should be about 4 inches.

[khoivo1]

i think it is smell like plastic or from water eval,,,maybe because a distance from water surface is too close i think it is 4inches above water surface,,,but i can't raise up any more unless i have to remove canopy,,,do you really have to be 6-8 inches from water surface? why?? my water temp is fine or it is too close thay why it is smelling,,??

[drummereef]

What light unit do you have exactly?

[khoivo1]

i have a combo light unit,,,with 2x175 double ended mh and 2x96wat actinic blue and some moon light,all in on unit,,,

[1F2FRFBF]

<a href=showthread.php?s=&postid=10107906#post10107906 target=_blank>Originally posted</a> by khoivo1
i think it is smell like plastic or from water eval,,,maybe because a distance from water surface is too close i think it is 4inches above water surface,,,but i can't raise up any more unless i have to remove canopy,,,do you really have to be 6-8 inches from water surface? why?? my water temp is fine or it is too close thay why it is smelling,,??
Maybe one of your bulbs is coming into contact with or getting too close to something else on your tank?

The way I understood it, you usually don't want your halides too close to the water for a few reasons - evaporation is one, increase in water temp is another, but there's also water splash and salt creep to consider (cooler water on a hot bulb can cause the bulb to burst, and salt creep building up on your bulb will cut the amount of light). Having your lights too close to the surface may also burn corals that you have up higher in the tank.

Another thing I just thought of - if the light canopy is new, that might also be why there's a plastic smell. New plastic will have a strong odor for a bit, and as time goes on it'll go away.