MH how high to hang?

[JonoB]

I have a 30 gallon long reef tank. It is 12x12x48. I bought all my stuff used from the same guy, and he had it set up so I could see everything before I bought it. When I got it home, I just hung the lights "about" where he had them, but he didn't actually have any coral in the tank so I don't know if he had them at the right place.

The light fixture is 2 150w metal halide lights, double ended, the 14k. If I plan on doing a mixed reef of lps, softies, and maybe some sps how high would you hang the lights from the water? Its a big heavy fixture so its kind of a pain in the rear to re-adjust.

Thanks.

 

[Crabs McJones]

Any idea how many inches the previous owner had them mounted? Being that is a shallow tank, you'll want to mount them higher. Best bet would be to get access to a par meter whether you purchase one or borrow one from a local reefer. You can also pick up a cheap lux meter and calculate par

 

[JonoB]

No idea, but here is a picture from the listing:


It just seemed really high for everything else I've seen, but I also realize that they are strong lights on a shallow tank. I'll see if I can get my hands on a par meter.

 

[CNDReef]

I’d probably put it somewhere between 12”-24” high.
I wouldn’t want all that light spill in my room

 

[jda]

Start at 8-12 inches and check out the spill. I would lower it until it stops most of the spilling, but do not get too much closer than 4" to the water.

If you let us know what kind of fixture it is and which bulbs are in it, I can get within 10% of PAR with guessing.

 

[JonoB]

I'll check when I get home, it is a fixture he wired up himself, but I can look at the ballasts and all that. It's the phoenix 14000k DE 150w bulbs. And yes, the light spill is awful right now

 

[JonoB]

I lowered it a few inches after this picture, but it's not that much different.

 

[jda]

If that were my tank, I would have that fixture like 8" off of the water.

 

[cracker]

Crabs has it right. A par meter would help out a lot .The height in the pic looks about right to me. I now see the second pic. There is a lot of light spill ! You won't have to turn on any other light in the room?

 

[JonoB]

Here are some pictures I jut took. I also measured, the lights are about 18" from the water.

 

[A. grandis]

Why the chains? You can use nylon cords instead.
Or even better to use those cables like the ATI cables.
I would say my halides would be between 5" and 10" from the water surface.
Fan between the water and the fixture to cut off the heat, as jda suggested long ago.

 

[JonoB]

Why the chains? You can use nylon cords instead.
Or even better to use those cables like the ATI cables.
I would say my halides would be between 5" and 10" from the water surface.
Fan between the water and the fixture to cut off the heat, as jda suggested long ago.

The chains because they came with it and they worked, never really thought about using anything else. They don't look bad and they hold it up.

I suppose I will look into bringing them closer. I've also been looking hard at LEDs today, I like the controllability, but these work fine so I dont know.

 

[A. grandis]

The chains because they came with it and they worked, never really thought about using anything else. They don't look bad and they hold it up.

I suppose I will look into bringing them closer. I've also been looking hard at LEDs today, I like the controllability, but these work fine so I dont know.

Don't look too hard! LOL! In most cases the LEDs' controllability becomes boring after a while and the less you have that the safer you will be. To have "total control" over and adjust light spectrum and intensity isn't necessarily a great thing. Besides, there is no LED that will supply the same spectrum and UV emitted by those halides. Halides are, in my opinion, the very best you can offer. Better than that only halides and T5s. Just my personal point of view.
Good luck.