Metal Halide light height?

[Fingers68]

I have a new 750 ltr setup with a twin 150w metal halide and 4 t5 light.

I have been told the height of the light should be round 12 inches off the water but I wonder as to why this can not be much lower ie 6 inches for eg.

Has anyone experimented and know from first experience about the height?

[ehren78]

You can do whatever you want, i've heard people only 4" above the water, me personally believe anywhere from 8" to 15" is good. Really it depends on the size of the tank, size of the pendant, I would set them up so there is no shadows in my tank. If you go low watch the Temp swings.

[Toddrtrex]

Assuming that you don't have to worry about heat, and splashing, you can have it as high or as low as you want.

There will be difference in the amount of light spread if you go higher or lower, but as long as you are happy with it, use whatever height you want.

Heck, the fixture over my 58 sits right on top of the tank trim. Whereas over my 75 the fixture is about 4 inches off the tank --- will be a bit higher once I get around to hanging it.

[thegrun]

6" is fine, in general the closer to the water the better, although 4" is about as close as I would recommend. You will need to acclimate any corals you currently have in your system if you do lower the light (lower the light 2" a week).

[imcosmokramer]

If your lights are to low, you'll run into two issues:

1. water temp in your tank will increase drastically
2. you will have a lot more salt creep on your lights.

You, of course, can manage both of those. Mine are about 8" above the water.

[Fingers68]

Thanks guys,

I wondered if there was issues with possible burning of corrals the closest corrals to the surface are about 8 inches under the water.

What would the signs be that I was too close for the corrals.?

[Toddrtrex]

<a href=showthread.php?s=&postid=14990529#post14990529 target=_blank>Originally posted</a> by Fingers68
Thanks guys,

I wondered if there was issues with possible burning of corrals the closest corrals to the surface are about 8 inches under the water.

What would the signs be that I was too close for the corrals.?

There is a possibility, but only if you didn't acclimate the corals to the lights.

The main sign would be bleaching of the coral.

In my 58 (( with 2*250 sitting ontop of the tank )) one of my corals is growing to the water surface, I would say it is less then a 1/4 inch from breaking through. It isn't bothered at all by my lights sitting right on the tank's trim. It would have been bothered if I had just got the lights, but since it is used to it, it isn't an issue.

[alextheromanian]

i have mine about 12....the issue that i comes down to is HEAT...

nothing more than that...i guess if you can keep your water at the right temperature and everything fine you can have the light an inch away.


i have mine set up 12 inches away this way i dont have heat fluctuations and have enough room to stick my arm...sometimes my head in the canopy without burning my face off hahaha

yes...it didnt occur to me at first but some things are hard to reach unless i stick my head inside of the canopy lol....

[drparker]

I've got two 150w Radium 20k bulbs with two 130w PC bulbs 7" over my 75G. Used to be 4" but I raised it during acclimation of new bulbs and will stay at this height since it should be easier to cool with just fans this summer.