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from what I've been reading, it seems T5 HO can be enough. I've seen beautiful setups using nothing more than T5 HO.

Is it because halide has that "rippling" effect? so people use halide mostly for aesthetics?

thank you
 

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I could imagine aesthetically it's because the super clean look and walk-around-the-tank ability of mH lighting. Tank maintenance is a little easier and from my own experience mH has a deeper, penetrating light than T5. I don't know if there's numbers to back that up hopefully others will provide some input.
 

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Mh is awesome for the "shimmer". aside from that, T5HO will do anything MH can do, but better lol. If you had a 36"+ deep tank, I'd say MH might penetrate a bit better, but most of us like a shallow tank with a lot of real estate rather than a tall beast like that.
 

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Fresh Fish Freak
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T5HOs give better light distribution on longer tanks than MH bulbs- simply b/c the bulbs themselves are so much longer. T5HOs also don't produce as much heat as MH's do, which is a serious consideration where I live, since chillers are so pricey.

You can definitely put together a nice planted tank with MHs, but you just need to compensate for their heat, light spread, and intensity right under the bulbs. Plus you really need to have good CO2 distribution in the tank.
 

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There are reasons for using MH lights - some people really like the way the tank looks with them. And, there are reasons for using T5HO lights - some people really like the way the tank looks with them. T5HO lights use less electric power than MH does. Most tanks are longer than they are in front to back depth, so a T5HO lights them more uniformly. Other than that I don't know of any compelling reason to use either one over the other.
 

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Thought I would throw my 2cents in here since I've got MH on the brain from the last post I replied to...

For the most part, MH and T5HO produce fundamentally different light spectrums. A MH with a high color rendition index will have a very smooth and "continuous" sepectrum that mimics sunlight - and the ratio of red wavelengths to blue wave lengths give this kind of light its "color temperature".

Fluorescent technologies (T5 and CF), however, do not produce a smooth continuous light spectrum - even if the bulb advertises "full spectrum". As such, these type of bulbs do not have a color temperature at all. They only have a "correlated" color temperature which is kind of like saying: "Well, this bulb sort of mimics a continuous-spectrum light source with "X" color temperature." Color scientists use a complicated mathematical color model to come up with a Correlated Color Temperature based on human perception and the human eye - which of course has almost nothing to do with plants! Plants simply care whether there are red and blue wavelengths in the light source, with sufficient intensity.

So whether a light source is useful for plants depends on whether the light source has ample red and blue wavelengths. I don't think there's any argument that both MH and T5HO produce excellent results with plants, so then the factors come down to light distribution, heat, efficiency (PAR/Watt), and aesthetics.

MH produces the highest photosynthetic active radiation (PAR) per watt of any light source that I've tested; From my tests, [STRIKE]far[/STRIKE] above T5HO, and significantly greater than other normal output fluorescent sources. This combination of PAR efficiency and continuous-full-spectrum is a plus for reef keepers: Since red light is easily absorbed by water (both salt and fresh), this allows the remaining ample blue wavelengths to penetrate into the deeper depths (3feet+).

In this regard, I don't think most people are going to see a difference with the shallow tanks that we use in planted aquaria.

But the cons of MH are the heat they produce and their uneven distribution of light into the tank. This is where fluorescent tubes (such as T5HO) excel with their cool running temperatures, small footprint, and long even light distribution.

Despite all of this, I would choose MH any day over fluorescent fixtures because metal halide bulbs (with high CRI) simply look like sunlight - both in light spectrum and point source distribution. Fluorescent technologies always make me feel a little bit "pale". I guess I'm sensitive like that.


Speaking of PAR per Watt
Here is a chart I made showing relative PAR values attained from different common light sources. "PAR" is the light that is available to plants for photosynthesis. A moderate value of light for aquatic plants measured in actual streams and lakes is about 120 PAR units. The table shows the wattage of the bulb and two PAR measurements taken at 1ft away from the bulb, and again at 2ft away from the bulb. Notice how they all pale in comparison to the MH wattage equivalents. [EDIT] T5HO is not in this chart... but the PAR values produced by T5HO fall somewhere in between CF and MH.


Cheers!
 

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Fresh Fish Freak
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Your data is pretty different from other PAR studies I've seen comparing MH vs T5HO (some online and some published). The PAR values on T5HOs with good individual reflectors (such as Tek, Solar, etc) usually are very similar if not exceeding MH, especially when measuring light distribution in areas other than just directly under the bulb.

I think age of the bulbs probably needs to be held constant, though- and I'm not sure that I've seen a published study that noted that possible variable.

Also- I don't see T5HO noted in your data? T5HO is very different from just standard flourescent fixtures (T8, T12...)
 

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Yes, my T5HO data did not make it into this older chart - which I prepared for a different reason. But I thought it relevant, so I included it even though it does not include T5HO. However, T5/T2/T8 HO are in the realm of Compact Fluorescent intensities based on my readings. Also, I've always found that published values tend to skew results based on the agenda of the published material. Not so much as "false numbers", but instead creating situations that are "ideal" for their tests/measurements. I did these real-world readings over the same tank, using the same water, and an appropriate reflector for each type of light.

[EDIT] I guess it also needs to be specified which MH bulb and ballast are being used. For example, I sought out non-aquarium MH bulbs from Philips in their Master Color Ceramic MH line with CRI's of 94+, with an electronic ballast by Advance. And I would agree that fluorescent tubes are ALWAYS better in the light distribution department. But, not so much, in terms of PAR/watt - at least, with the bulbs/ballast I use.

Maybe I'll add VHO measurements to the chart when I get setup at my new place. I have all the parts and pieces, I just need the time :)

Cheers!
 

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Thanks for sharing that info. Here is my subjective 2 cents having used a pair of 175 watt MH pendents over my 55 for 10 years or so. They generate a lot of heat-so much in fact that I've always toyed with the idea of getting a small chiller. The bulbs are hard to find locally and are expensive-also they don't seem to last very long. The ballasts need replacing periodically as do the sockets. If you don't have back up parts your plants will go without light while you wait for UPS to arrive. That being said, they do look nice, specifically the light they provide. I got tired of replacing bulbs and rebuilding ballasts-I now have a Hagen GLO T5 fixture and I'll no longer look lustingly at chillers in catalogs.
 

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Excellent post as always, 4x4. You definitely almost have me convinced to use MH over my tank that I'll be setting up shortly. What you said makes perfect sense about the blending between different wavelengths of light that MH has as opposed to fluorescent lights, and that never occurred to me. :) :thumbsup:
 

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Thanks for sharing that info. Here is my subjective 2 cents having used a pair of 175 watt MH pendents over my 55 for 10 years or so. They generate a lot of heat-so much in fact that I've always toyed with the idea of getting a small chiller. The bulbs are hard to find locally and are expensive-also they don't seem to last very long. The ballasts need replacing periodically as do the sockets. If you don't have back up parts your plants will go without light while you wait for UPS to arrive. That being said, they do look nice, specifically the light they provide. I got tired of replacing bulbs and rebuilding ballasts-I now have a Hagen GLO T5 fixture and I'll no longer look lustingly at chillers in catalogs.
Yes, I hear you... I had to get a 1/4hp chiller to put on my 15gal planted tank because of the heat from the MH's. <Grin> But I look at it this way... now if I ever decide to do a salt water tank, I'm set. However, I am curious about all your maintenance issues with your MH's. I've been running mine for the last six years and I've only had to replace the bulbs every few years. Were you using electronic ballasts? And yes, I totally agree, you have to think ahead and plan for when you are going to need parts. The bulbs I decided on are VERY hard to find ANYWHERE... I end up having to order them directly from Philips.

Excellent post as always, 4x4. You definitely almost have me convinced to use MH over my tank that I'll be setting up shortly. What you said makes perfect sense about the blending between different wavelengths of light that MH has as opposed to fluorescent lights, and that never occurred to me. :) :thumbsup:
Thanks CL... Well, if you decide to go down that route understand that heat is a huge issue. Even in an air conditioned room, MH's dump too much heat into the water. It might be somewhat less of an issue with larger tanks (100gal+), but with the smaller variety the lights have to be well vented and fan cooled... to the extreme of using a chiller. And I cannot overstress that all MH bulbs are not created equal. They come in many different forms to meet the needs of several different industries, mostly which revolves around commercial and industrial lighting. When shopping for MH bulbs, choose bulbs that have a high color rendition index, preferably above 90CRI (100 is the max, and if a MH bulb was rated at 100CRI, it would perfectly match sunlight.) I coudln't find what I was looking for in most MH lights designed for aquariums which is why I went the complete DIY route... and any which way you look at it, it is expensive. Also, most of the MH lights you see on reef tanks do not have the sunlight quality I am refering to, they are shifted heavily blue/green - perhaps because of their efficiency of penetrating deeper waters, or simply perhaps because they are cheaper to make.


15gal With 120W MH
Sorry to rehash old images... but here's my 15gal with 120W of MH... notice the chiller on the side of the lower cabinet :)
 

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T5HOs also don't produce as much heat as MH's do,
the cons of MH are the heat they produce and their uneven distribution of light into the tank.
T5HOs and MHs have similar efficiency. Some of the power put in is converted into light and most is converted into heat. I.e.: same power bulbs (one of each), similar light and similar heat.

The issue is that MHs get hot in one spot whereas T5HOs are spread out and the air takes the heat away so much more quickly.

To push a point, where MHs are just slightly more efficient and furthermore produce just slightly more useable wavelengths one could say that for similar growth of the plants, MHs in fact produce less heat.
 

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Is it true that mh bulbs should be replaced every 6 months? I love the shimmering effect but, the cost of mh is just daunting.
 

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Yes, I hear you... I had to get a 1/4hp chiller to put on my 15gal planted tank because of the heat from the MH's. <Grin> But I look at it this way... now if I ever decide to do a salt water tank, I'm set. However, I am curious about all your maintenance issues with your MH's. I've been running mine for the last six years and I've only had to replace the bulbs every few years. Were you using electronic ballasts? And yes, I totally agree, you have to think ahead and plan for when you are going to need parts. The bulbs I decided on are VERY hard to find ANYWHERE... I end up having to order them directly from Philips.
No, they aren't electronic. I would imagine that they are less problematic. Perhaps my problems are age related-they are at least 10 years old. Connections in the sockets get corroded, the plastic grommets that hold the cord in the top (and supports the fixture) get brittle/crack and become non-functional. They are finicky about being slighlty underpowered eg: at home the 111-112 volts at my outlet won't fire them on while if plugged into a good 115v outlet they will. Good bulbs are expensive. As another poster said they are not hotter than fluorescent-maybe not per watt. But to cover a 4 foot wide tank you need 2 fixtures and a 175 mh pendent does get hot-very hot. I do love the look of them though.
 

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T5HOs and MHs have similar efficiency. Some of the power put in is converted into light and most is converted into heat. I.e.: same power bulbs (one of each), similar light and similar heat.

The issue is that MHs get hot in one spot whereas T5HOs are spread out and the air takes the heat away so much more quickly.

To push a point, where MHs are just slightly more efficient and furthermore produce just slightly more useable wavelengths one could say that for similar growth of the plants, MHs in fact produce less heat.
Touche :icon_wink

Though in terms of practical use- the point still stands that heat transferrance to the tank is as not as big an isssue when working with T5HOs rather than MHs.

Overheating tanks (especially during the summer months) is a serious issue where I live, so is a big consideration when I go to select a light fixture.

In other situations, the heat from MHs may be an advantage.
 

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Oh, OK. It's only 80-85F here at the moment.

I have a 1 foot canopy space above my 125 with a trio of 70W halides. When I slip behind the curtains to skim the surface, it's barely warm, though I do need to wear sunglasses :icon_wink: My ballasts are mounted outside the canopy.
 

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Is it true that mh bulbs should be replaced every 6 months? I love the shimmering effect but, the cost of mh is just daunting.
I do not replace mine every six months. But the warning is this: Some MH bulb types (ED17, for example) simply do not "go out" at the end of their life.... they explode, or CAN explode. This is why most bulbs have to be in a rated enclosed fixture. Commercial applications of MH bulbs have a routine replacement schedule to avoid the problem of exploding bulbs, think your local Costco or HomeDepot which use MH bulbs located in the rafters.

When bulb manufacturers specify a life span (in hours) of a MH bulb, what that means is this: they started with "X" number of bulbs burning continuously, and after a period of time when half of them have expired and half are remaining lit, they say THAT amount of time is the rated life of their bulbs. Therefore, if you replace your bulbs before that amount of time, you are likely to avoid the problems associated with expiring MH bulbs.

Thus, bulbs that are rated for 10000 hours, for example, should be replaced every year if you run them 24 hours a day, or every 2 years if you run them 12 hours a day. Or you can just wait for them to expire and hope the potential of an exploding bulb doesn't cause any damage or start a fire.

That being said, my particular Philips Master Color bulbs have been running for four years+ for 12 hours/day and they still produce the same PAR they did when they were new.

I can't speak for HQI bulbs, only ED17.

I'm curious: Has anyone ever had an "exploding" MH bulb? Mine are in rated fixtures, but it is something that lingers in the back of my mind when I'm gone at work for 10 of those 12 hours that the tank lights are on for.

Cheers.
 

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4x4, just wondering if you ever have some crazy algae outbreaks or a lot of maintenance with that much light?
Sure, I've had my learning curve with algae. But once I learned about the mechanics of a proper substrate, and about PAR values, algae is now very minimal. Usually what gets me is that I don't trim and prune enough. I love to see the vibrant growth and don't want to cut a plant down, but soon the large plant mass shifts the dynamics of the tank. It changes the water flow, and hence the CO2 distribution; and it changes the amount of light reaching the lower plants. And, it creates excessive dissolved organic carbon, from decomposing plant matter.

But you say, "that much light"... remember 70umols/m2/sec is not excessive light for plants, it's at the lower end of "moderate". I know it's easy to think "metal halide" and conclude "wow, a lot of light". But it doesn't matter how the light is created (MH, T5HO, CF, or Incandescent) or what the wattage of the bulb is.... 70umoles/m2/sec is 70umoles/m2/sec of photosynthetic light.

I used to plants non-CO2 tanks with 120umoles/m2/sec but the plants grew too fast, and eventually it overdrove my soil's ability to provide nutrients and CO2. That led to algae. So, I just raised the light in incremental steps... to reduce the PAR values by -10umoles/m2/sec each time. I stopped raising the light when the glosso would no longer grow horizontal at the bottom of the tank... Incidentally, that's why I now target 70umoles/m2/sec at the bottom of any new tank I setup - and tweak from there. For example, a thick carpet of HC can go as low as 50umoles/m2/sec of light and still spread nicely. But, ludwigia repens needs about 100umoles/m2/sec to turn, and stay, red. Riccia also seems to have a melting threshold with light below 65umoles/m2/sec in a nonCO2 tank.

So, in short, the only time I get "crazy" outbreaks of algae is when I induce it intentionally... which I do from time to time for learning purposes.
 
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