# Metal Halide Vs Flourescent



## Aeropars (Apr 20, 2006)

Whats the advantage of going hetal halide? 

I've seen combo lamps around mixing MH with flourescent.

Any comments on these?


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## gf225 (Mar 26, 2005)

MH is arguably more aesthetically pleasing due to the intensity creating a spot light effect and consequent shadows, ripples etc. They are usually mounted over open topped tanks using lumanaires, so a hoodless, braceless, rimless aquarium is probably the best choice. 

Most planted MH is 150w, although 70w and 250w are used. 400w and 1000w are also available but generally used for reef. I wouldn't personally put a 150w on anything less than 30G. 

I think the general rule of thumb is 1 x 150w per 24" length of tank. 1 x 150w with 2 x 24w T5 would be ideal for a 90x45x45cm / 36x18x18" (180 l. / 50G) 

I would personally use MH in conjunction with fluorescent, running the MH for 6 hours or so in the middle of the total photoperiod, with the fluorescent running the whole time.

MH is generally more expensive than fluorescent and creates more heat, that can be an issue in the hot British summers.

Another issue for some is light spill. MH is usually suspended 30cm+ above the water. Depending on unit you may find the light quite distracting/dominating, if there is lots of spill.

In the UK, Arcadia, Giesemann, Aqua One and Aqua Medic all supply a range of units.


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## AaronT (Apr 26, 2004)

MH is also thought to penetrate deeper tanks better.


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## erik Loza (Feb 6, 2006)

I use both. Your question is quite open-ended. What size tank(s) do you have, what are your goals in terms of plant life, what kind of space do you have to work with, and how much do you want to spend? These would be more important questions to answer, first. Good luck.


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## ruki (Jul 4, 2006)

Metal halide lamps provide a narrow beam focus to the light because of how the bulbs are constructed. This spot light effect will penetrate better than more spread out lights. These also provide more light per watt than fluorescent. 

Haven't used them yet because the hot spots the new smaller ones generate aren't really appropriate in racks. Also, when mixing them with flourescent fixtures, the heat from the metal halide bulbs in the new mixed fixtures could shorten the life of flourescent tubes.

The traditional pendant form of these lamps can be very appropriate for indoor ponds and large show tanks.


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## NE (Dec 10, 2004)

MH might penetrate the water better but the narrow beam also causes heavy shadows if plants get in the way of the light.

I used to have MH and the light effects is very similar to that of the sun and that is nice, but i have now changed to T5 and it's a different light but i cant say which is the best.
T5 is nice because give an even light which is not to easily shadowed and it's dimmable.

I have it dimming in and out to simulate sunrise and sunset, that is nice  .


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## Laith (Sep 4, 2004)

NE said:


> ...
> T5 is nice because give an even light which is not to easily shadowed and it's dimmable.
> 
> I have it dimming in and out to simulate sunrise and sunset, that is nice  .


Yes, that is a nice functionality. 

However I just wanted to note that you have to have special ballasts to be able to dim T5s; you can't just add a dimmer switch to a normal T5 installation, so don't try that!


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## NE (Dec 10, 2004)

Laith said:


> However I just wanted to note that you have to have special ballasts to be able to dim T5s; you can't just add a dimmer switch to a normal T5 installation, so don't try that!


Thats true, you need equipment made for it.


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## ruki (Jul 4, 2006)

Hmmmm....

I wonder if dimming shortens the life of tubes?

Sounds really cool (and expensive though)!


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