Who told us to change MH bulbs once a year?

[Mark Spencer]

After 2 weeks of the new bulbs being in place I have to admit that I see a dramatic slowdown in the growth of hair algae, the latter of which became a nuisance about two months ago. I was very skeptical that bulbs would make a difference and I realize that my observations make for anecdotal evidence and not proof in any way.
As to the comment that nutrients cause algae blooms: I agree but the problem is that even a concentration of phosphate that is lower than the detectable level of a test kit is enough to fuel algae. I only have to look inside my overflows to see a veritable forest of algae to know that my aquarium will never have nutrients that are so low that there will not be the potential for algae growth. What keeps it manageable is biological control in the form of snails, hermits, crabs, tangs, blennies, etc.
I also know that algae absorb different wavelengths of light from the xooxanthallae algae that fuel coral and that, therefore, the spectrum of light produced by bulbs will make a difference in algae growth. Just how different is the big question.
Maybe someone who has seen studies of absorption spectra of light by microalgae (especially hair algae), macroalgae (such as in the refugium) and xooxanthallae can clue us in.
Mark

[Nathan]

light7,

I'll see what I can do regarding pics this weekend. (My hood isn't very accessable).

I upgraded from my BEAUTIFUL 75g when I moved to Pennsylvania. Kept most of the equipment including MH bulbs.

My tank is 180g (been set up for 3 months only), 3 Chromis, 1 butterfly, 1 angel. Since I had to start all over again with the corals I am SLOWLY building them up again. I have only a handful of corals now.

-Nathan

[dnjan]

If your replacement bulbs were the same brand and color temp, then the intensities of the various wavelengths should be equal or greater for the new bulbs as compared to the old ones (within the variability of the bulb manufacturer). So the reduced hair algae would not be because the new bulbs have less intensity at certain wavelengths.

Therefore, the reduced hair algae is probably due to something else (beneficial xooxanthallae in the corals?) outcompeting the hair algae for nutrients, due to improved intensities at the preferred wavelengths of the xooxanthallae. The reduced hair algae is therefore a secondary effect, but a noticable effect just the same.

[Mark Spencer]

I think we're saying the same thing. After the mild confusion over Sanjay's findings with aging bulbs it seems clear that, as a bulb ages, it loses intensity at the shorter wavelengths. That is equivalent to saying that the color temperature drifts toward lower temperatures. So a bulb that is sold as 10,000 K may, after a year of use, have an actual color temperature of 7000 K. We know from setting up refugia that the macroalgae (caluerpa or chaetomorpha) in the tank grow best with 6500 K bulbs. Therefore, if microalgae absorb light similarly, then they will gain a competitive advantage as the MH bulbs age and become "warmer." So it makes sense that aging bulbs would foster nuisance algae growth.
Just a theory at this point.
Mark

[Nathan]

Has anyone replaced a one year or older 10K bulb and experienced the sort of major colour difference that people here are talking about (ie, 7000K (old) to 10,000K (new))?

I have used a number of combinations of bulbs, but every time I have used a 10K (both Ushio and XM) the colour is ALMOST exactly the same; just the intensity of the old bulb is less due to the blackening near the electrodes.

I have never had a 10K bulb go "yellow" on me. (7000K is very close to 6500K (Iwasaki) and I am telling you that my 5 year old Ushio looks NOTHING like an Iwasaki).

I'll take a pic this weekend to show you.

-Nathan

PS One way to explain light vs. algae, you can say that light is a CATALYST for algae growth in tanks that have excess nutrients. (ie, a tank with nutrients and no ligth won't grow algae, a tank with light and no nutrients won't grow algae, but a tank with both light and nutrients will grow algae). So therefore light AND nutrients are the "enablers" or catalyst for algae growth.

[Nathan]

Also, for those who still belive that colour is what leads to algae growth, what about this question:

Which bulb will lead to more algae growth:

a. 400W 10K
b. 175W 5500K

?

-Nathan

PS In my opinion it's the INTENSITY of the light that plays a major role in algae growth; there has to be some sort of threshold; I don't think it's exactly a linear proportional relationship. It would be interesting to study though.

[dnjan]

Originally posted by Nathan
Also, for those who still belive that colour is what leads to algae growth, what about this question:

Which bulb will lead to more algae growth:

a. 400W 10K
b. 175W 5500K

?

-Nathan

PS In my opinion it's the INTENSITY of the light that plays a major role in algae growth; there has to be some sort of threshold; I don't think it's exactly a linear proportional relationship. It would be interesting to study though.

Actually, it is the intensity of the light at the wavelengths preferred by a specific algae that plays a major role.

Talking about color temperature is a convenient way to categorize MH bulbs, but when we want to talk about specific (growth) issues, it is better to shift the conversation over to wavelengths. So, a 400w 10k bulb could have more intensity at specific yellow-red wavelengths than a 175w 5500k bulb.

[Mark Spencer]

Nathan has it right.
We would have to look at how algae absorbs light. That information is in the form of an absorption spectrum, i.e. the percentage of light that is absorbed as a function of wavelength. Green plants are green because chlorophyll absorbs the spectral components of light on the red end AND the blue end (thus reflecting green which is in the middle). All plants, from microalgae to trees, will have a different absorption spectrum depending on the environment of the chlorophyl molecules. Pigments that are found in coral will shift the wavelengths that the xooxanthallae absorb.
After we have the absorption spectrum of the coral or algae in question we next have to look at the emission spectra of the light source(s) which shows the intensity of light given off as a function of wavelength. If we lay the emission spectrum of a given bulb on top of the absoprtion spectrum for the species in question we can which wavelengths of the bulb are absorbed most by the plant or animal. This can all be done quantitatively and forms the basis of Sanjay's newly defined term, PUR, or photosynthetically useable radiation. So if, for example, an algae abosrbs strongly at the red wavelengths then we compare the output of two lamps (old vs. new or 6500 K vs. 10,000 K) and see which bulb's emission spectrum has more intensity at the red wavelengths.
Give us the spectra with real numbers and we can answer anything!
Mark

[Nathan]

Hahhaha Mark!!!

You go man!

Isn't it funny though, no matter what the heck kind of equation/theory we come up with, my corals are still going to grow no matter what even if I have those dreaded Iwasaki's or even if I get 4300K MH bulbs from HomeDepot! Humans just over analyze! But that's in our nature since we can't be satisfied until we have "figured it out". (Hope there are no women listening to our stereotypical "masculine" way of thinking!) (Maybe my wife has been watching Dr. Phil too much! )

Have a good weekend!

-Nathan

[The Grim Reefer]

Nathan,

Perhaps you can hook up with Sanjay and let him put your 5 year old lamp under the spectrometer. That would be very interesting to see just how much the color has changed. I don't think there would be too many 5 year old lamps around for a test subject.

[Mark Spencer]

I had a friend who had a 90 gallon reef tank that served as my inspiration when I was getting into the hobby. He died suddenly 4 years ago and his wife took over the tank and did next to nothing. No water changes (except for topping off). No supplements. No bulb changes. Almost never changed the protein skimmer. The tank was still doing well last time I checked. I, on the other hand, started off with a tank in which things died on a weekly basis in spite of doing hours of maintenance a week. When I switched over to my current tank my problems ended. A lot of things about the tank were different but it's impossible to say if one or more of them were responsible for the turnaround.
This hobby is still more art than science. There is an explanation for everything but we are rarely know the explanation.

[Mark Spencer]

Although this prolific thread ended last month I feel duty bound to correct an erroneous finding that I reported. I had been having a recent hair algae outbreak after being free of the stuff for a year. After I changed my MH bulbs I reported a slowdown of the hair algae. Unfortunately I have to withdraw that claim as the algae has since accelerated its growth. It's now a serious problem. I can therefore not support the hypothesis that aging bulbs cause algae outbreaks.
Just when I think I have it all figured out...

[Bomber]

Mark, all my bulbs are almost three years old right now and I have no hair algae.

[Clayman]

Think of it this way if a light losses only 20% of it's output, that's 20% that YOUR are paying for and not getting. If you ran a bulb that had a 20% loss over a one years time your have flushed all that money down the toilet, keeping it going rather than chaniging it out for a freash bulb. As HID's get old the use a tad more power as the bulb burns slighty hotter and not as bright. But I still would not chage every 12 months, BUT I would start changing around the 18-24 month mark. See here power is cheap around 5 cents (CAD) a kilowatt/hour and I have seen some of you huys in the US can pay more than 10 cents. It's your money and you should get what you are paying for. Just my 2 cents

[Micki]

What about actinic lights. What would/should the time be for those? I'm talking PC actinic.

[Savatage]

I'm tagging along also. I am in the process of purchasing a used PC fixture. 4 x 96 watt bulbs and if they're used or used up, the cost for 4 new bulbs is 200.00. I don't want that kind of bill.

[sradmin]

orginally posted by Mark Spencer

This hobby is still more art than science. There is an explanation for everything but we are rarely know the explanation

So true... Those two sentences should be somebody's tag line!


The nutrient pathways in any given tank are dynamic and always in a state of flux- and how could anyone ever fully quantify the competition between organisms in an average reef aquarium?

There are a handful of members on this board and in this hobby who've brought volumes of knowledge and theory from their schooling and careers- the rest of what we have (mostly) are techniques and methodologies honed through years and years of trial and error. While I have taken a pretty good amount of college level chem and bio courses, I am still just an average hobbyist- and my tank is far more a work of art (expression) than it is a controlled study or science experiment.

Getting back on topic, though... I am using a not quite four year old 250 watt Iwasaki (am I cheap or what?) with 56 watts of 420nm/460nm PC- just enough blue to balance out the yellow of the 'waki to my liking. There is a significant amount of macroalgae that grows in my display (Botryocladia and Chaetomorpha). Periodically, I have to remove large amounts of Botryocladia from the overflow bulkhead, strainer, and powerheads. Other times I have to pull a clump of the chaeto out. Each harvesting of the macros will (apparently) allow a small clump of Bryopsis to temporarily gain a foothold, usually in an area of both higher detrital accumulation and strong light. This is a cycle I can repeat with predictable results each time, and have been doing over a period of roughly 18 months. This indicates to me that the bulb spectrum has little effect on what type of algae grows- but that competition for nutrients (availability) is the limiting factor.

I am not suggesting that algaes don't have lighting preferences, but I think those preferences are secondary to available nutrients (necessities).

Great discussion!

[MadTownMax]

right-on steve - nice real-world input

compact flourescents have a straight line of decreasing output - so you'll slowly be loosing output over about 7 months (give or take depending on the usual 8-12 hour lighting period) then you'll have to replace them. That's basically why halides are so much more cost effective - replacement costs for PC's is about 2X as much (or more, if halides really do last for more than a year)- once you're looking at keeping a larger tank (or just want enough light for sps or clams - or other light-loving corals)

[Savatage]

If you look at the total overall power consumption and cost of bulbs with MH and do the same with PC lighting, I think it is still cheaper tp run PC lighting. For a guy like me who don't find a need for SPS or clams. At this stage of my experience. I've only been doing this for 9 or 10 months.

PC lighting saves so much energy. MH sucks you dry on the electric bill. Correct me if I'm wrong. This is more of a question than a statement.

[MadTownMax]

Cost comparison is all dependent on what system you're planning.



For your situation(75-gallon), some people would run 4X 65W power compacts, for a total of 260 watts, which linearly degrade to 60-70% of their original output over 7 months (average - just my own personal findings)

An alternate system would be to run two 70-watt halide bulbs, for a total of 140 watts - since the bulbs are double ended, they last for 18 months on average (assuming an average 10-hour photo period) so you are only buying one bulb instead of three during that time.

Halide light penetrates deeper into the water due to it's nature (High-intensity-discharge) - so you are actually getting more useful light deeper into the tank, compared to PC's, using half of the electricity...

You'd have to look at comparative data to see the hard numbers for comparison (Lumens at different depths for PC's and Halides over time) There is an article posted somewhere from a conference that took reading of Halide lights, PCs and some others in various tanks at different depths - I don't know if the age of the bulbs was disclosed, but I think they were mostly new)


and then back to the point of this thread - how quickly halides actually decrease in light output - the 18 months is just an estimate set by the manufacturer - you may be able to get much more lifetime out of these bulbs (as you can see from those who are doing it in the posts above)

anyone reading this thread definatly needs to check out www.advancedaquarist.com and read through Sanjay Yoshi's metal halide bulb testing and see the actual degradation over time of halides -

http://www.personal.psu.edu/faculty/...lideLamps3.htm

especially one like this that shows the inconsistencies from bulb to bulb - explaining why there are so many mixed opinions and observaitons - leading back to variability in bulb quality

[Savatage]

I know I need good lighting right now, but can't afford the metal halides. Eventually I will be getting MH. That's a plus. For now I have to stick with the PC though. Thanks for your input.

[The Grim Reefer]

If you want low operating costs get T5's. They will be effective for at least 18 months and put way more light in the tankthan VHO or PC's using less power.

I don't remember if I posted this eariler in this thread or another but here it goes again. Lamps change there intensity and spectrum as they age. It's one thing for a coral to slowly adapt to a lamps changing output over a few years but what happens when you suddenly hit them with new lamps? Hopefully Sanjay can get some old lamps to run tests on.

[wonrib00]

Savatage: Save your money and get the MH. I just switched from T5s, and I can not believe the difference. Stay with the PC until you have the funds for the MH, it will be cheeper, and a lot less heart ache.

[Savatage]

Thanks. Right now I can pick up a PC 4 x 96 watt for under 200 bucks from a guy near me. I will buy that and wait for getting the MH.

[Mark Spencer]

I suppose a good thread can have more than one life. I'm glad to see the diversity of responses to the aging of bulbs. Given a large enough sampling size we can use statistics to come up with meaningful answsers. It seems that 18 months is a good estimate for the replacement period for metal halide bulbs. This is consistent with the 20% decrease that I measured with my light meter after 14 months of use. Sanjay's data, though still wrought with uncertainties (due to not having new bulbs to test), supports this time period.
I have learned much from so many great responses. I have noticed some comments that are not rigorously true. I will just bring them up so we can accept the vast majority of the responses as true statements.
1. MH lights don't penetrate deeper into the water. A photon is a photon whether it came from a PC bulb or a MH one. Two lights with the same spectral distribution will penetrate water exactly alike.
2. You won't get more for your money by replacing a bulb that has lost 20% of its intensity. I know because I wrote a check for $300 for 3 bulbs. We know that the spectral distribution shifts toward the red as bulbs age and that we need to know when the shift is large enough to affect the health of our corals. Sanjay's testing of bulbs to measure the spectra of aging bulbs, together with his newfangled quantity, photosynthetically useable radiation (PUR), will give us the answer.
3. I reiterate that I made a statement that is dead wrong when I reported that hair algae growth subsided with new bulbs. My hair algae growth is accelerating after being in check for months but I would attribute that to an increase in nutrients. Bomber's reply that his bulbs are 3 years old and that he has no algae is a validation of his bare bottom tank's ability to keep nutrient levels low.
Mark