More Lighting Questions...Glass Top


New member
I just recently went metal halide on my 36 gal bow front corner tank. I just started the aquarium in the anticipation that I will put corals in it. The light is a 150w 14,000K HQI. Its a beautiful light, but Im wondering if the glass top to the aquarium is refracting a lot of the light. Is this true? If so, would an acrylic top absorp more of the light . I would rather place the light on the aquarium with docking legs than to remove the glass top and suspend the light from the ceiling if at all possible. What are some suggestions?? Thanks
The glass top will refract and cut down on the lightings intensity, plus the glass top will also hold in heat, and wont allow for proper gas exchange to take place. If the halide is too close to the glass top it can shatter from heat
I would actually ditch the glass top all together, and place the hailde atleast 6 inches off the water surface. If thehalide doesnt have a splash guard I would go even higher.
A clean glass top will reduce the lighting by about 12% or so. Clear acrylic will aborb less, around 8%, I think. You can find numbers like these at tank-builders sites. Since it's a 150 W lamp, I would guess you might be fine with a glass top. I'd watch the temperature in the tank carefully, though, and make sure there's some gaps at the edges of the top to allow air into the tank.

I think my MH lamp is about 8" off the water (150 W over a 29g), with no top, though. 14" sounds like a lot of lost light to me.