Light position in this case

I have a 175w MH pendant w/ a bell shaped reflector (white on the inside) from Hamilton and my situation is I have a 3/8" thick glass siliconed in the middle of the tank...is it better to put it up higher above open water (6" ?) or put it on the glass plateform for max. benefit of the light?

The top of the glass plateform is about 1.5" above water surface.

Thanks!
GKW

 

usually if you dont want heat issues put it about 8-12" above the water but 6" is good to if you dont get heat issues now as for the glass on top of the tank never used it seem to affect the light penetration into the tank and i just never used them again.

 

That's the thing that's worry me, light penetration. This tank looks like it was build with no center brace, but the previous owner silicon the glass in the middle (about 18 inches long). So, I don't know if I should remove the glass or just not put a MH above that (no corals underneath of course). It will has 80w T5-HO across the tank.

Thanks!

 

My hunch would be 6-8 inches above it.

I don't think those pendants are designed to sit on glass. I think it might trap too much heat.

Plus the light won't spread too well.

 

Actually, the bell reflector came with a glass bottom...it can be screw on. I am also aware of the heat build up in the bell reflector, but if it's suppose to be enclosed, then would it place on the glass be a problem?

I don't know what to do. I want to place the light in the center of the tank, but the glass is in the way and will reduce light penetration...would placing it so close to the water make up for the reduce light penetration???

Thanks in advance!
GKW

 

Raising it will cause a loss in intensity but allow for more spread and less heat. It's a trade off. You will need to tinker around. If you set it on the glass you won't get much spread at all so all your light intense corals would have to be right in the center.

 

I think the best thing to do is replace the frame. Do you or anybody know where I can get the top frame with the center brace?

Thanks!

 

I wouldn't go to that extreme. The glass brace will be better than anything else you will find.

I would just raise the light until it covers the entire tank.
BTW MH light run hot, then like to be hot. It is not the bulb heat we are concerned about but the heat transfer to the water.


J