Old Bulbs = Algae

[Werbo]

I understand that older bulb lose intensity and there's a slight spectrum change. I've heard that old MH bulbs can be a contributing factor to unwanted algae growth. Could someone explain the theory behind algae growth?

[Myka]

The reason for the algae growth is because most bulbs will actually have a fairly significant spectrum change. The spectrum goes red, yellow, white, blue. Not sure what red is (0K?), but yellow is 5000K, white is 10,000K, and blue is 20,000K. Everything in between is in between (go figure!). Whatever color it starts as (blue or white) it will fade towards the red spectrum. A new bulb being 20,000K may be 16,000K after a year. A new bulb being 10,000K may fade to 7,000K. Each bulb will fade a bit more or a bit less than the next bulb, and the ballast will also influence. The red spectrum encourages plant growth, that is why horticulture bulbs are low Kelvin like 5500-6500K.

[randallino]

What effect does age have on T5 fluorescents?

[Myka]

Same thing, but quicker. It's the same for all bulbs, including household bulbs. To avoid this spectrum fade it is wise to change bulbs at certain times according to the type of bulb:

Halides 12 months
T5HO 8 months
Compact Fluorescent 6 months
VHO 12 months

Over-driving the bulbs will cause them to fade faster, like say using a mogul halide bulb on an HQI ballast. Using fans on the bulbs to keep them as cool as possible will help them perform better in their usable life as well.

[chris88]

The spectrum and intensity does change in various lighting bulbs but its not the major causes of an algae bloom. Algae will grow because there is an access of nutrients. You could put a ton of red over a tank will low nutrients and no algae will grow. In fact that’s what people are doing with the new fiji purple and ati purple plus bulbs, they are adding red spectrum. If you have excess algae growth you will have access nutrients (nitrates, phosphates, silica, etc). However, the added red and yellow spectrum will make a high nutrient tank grow algae much faster because algae use red spectrum very well for photosynthesis.

[2pts]

Now my algae growth makes sense, lol

[MrGoodbytes]

Not sure what red is (0K?), but yellow is 5000K, ...

Not exaclty the answer to what the OP asked but I thought I would post this for curiosity's sake. The colour temperature (as some may know) corresponds to the peak wavelength of the radiation of a blackbody at that temperature. To find this wavelength (should you be so inclined), you can use Wien's Displacement Law:

wavelength (meters) = 0.002898 / temperature (Kelvin)

So a peak of 700 nm (very red) corresponds to about 4,140 K.

[chris88]

To make it really simple. Algae need a few things to survive and thrive.
-They need light to photosynthesize (especially red light or low kelvin color light like 6,500k or lower)
-They need nitrates, fish crap and decomposing waste, some water sources can have high nitrates to begin with
-They need phosphates, most flake and frozen food, sometimes from tap water or a bad ro membrane.
- And sometimes certain algae use silica to their advantage (mostly diatoms)

If you are getting an algae bloom and your bulbs are old it will not necessarily fix the problem. It might help if you get new higher Kelvin bulbs like 14,000k or 20,000k but they real key to eliminating algae is to lower your nutrients. Try reading about carbon dosing, increase your water changes, feed less, get a bigger skimmer, etc.

[Myka]

Not exaclty the answer to what the OP asked but I thought I would post this for curiosity's sake.

So a peak of 700 nm (very red) corresponds to about 4,140 K.

Thank you for posting this, but it doesn't make sense...? I have some household bulbs that say 3500K on them and they are not red. Am I missing something?

----------------------------

Chris, the OP didn't ask "why do I have algae?". The OP may not have any algae at all. The OP asked "I've heard that old MH bulbs can be a contributing factor to unwanted algae growth. Could someone explain the theory behind algae growth?" There are nuisance algae threads all over the place (my signature for example lol).

[Bloodasp]

Doesn't make sense either. Graphs I've looked at show red being at 1000-2000k

[chris88]

You can't really compare Nm to kelvin. Red is from 650-700nm but that doesn’t correlate to a Kelvin tempter. A lower Kelvin light will have more red in its spectrum but that doesn't mean the bulb is going to look red. Just like a 10,000k bulb has a lot of green light, it doesn’t mean the bulb looks green. A 2,700k bulb will have a warm oranage-ish yellow hue almost like a candle light, while a 20,000k barely has any red spectrum in it and is predominantly blue. Most mid range bulbs have spikes in different spectrums which makes the color look white because of the way they blend. (6,500k – 14,000k)

[MrGoodbytes]

Hmm interesting. I looked into it further with respect to fluorescent lamps in particular and it turns out to be quite a bit more complicated to determine actual correlated colour temperature (CCT). They use CCT to distinguish between actual CT since our lamps aren't actually radiating at that temperature.

You can use Wien's Law to find the peak of the blackbody spectrum which that of the lamp resembles but the lamp's spectral distribution (intensity per unit wavelength) will be different, due to the phosphors. Nevertheless, it still produces light that looks similar to our eyes, which "add" colours. That's why a low CCT lamp may appear white-"ish" but have a peak in the red - the other colours are playing a part when we observe them altogether.

Bah, sorry if this is way off topic or anything. Hope this clears things up somewhat.

Graeme

[Myka]

Graeme, it is still interesting information that's kinda on-topic. :p the bulbs we use are usually "rated" at a certain color temperature, but if you use a CT meter it will say the color is much different. I don't fully understand why we see it as a different CT than the meter does? Must have something to do with the spikes in the spectrum over-powering our eyes maybe...?

Just like a 10,000k bulb has a lot of green light, it doesn’t mean the bulb looks green. A 2,700k bulb will have a warm oranage-ish yellow hue almost like a candle light, while a 20,000k barely has any red spectrum in it and is predominantly blue. Most mid range bulbs have spikes in different spectrums...

That's why they are called "full spectrum". Some are "fuller" than others though. I think most people know that all the colors in the rainbow are in "white" light.

[RuGlu6]

My T5 bulbs are 3+ years old. Replaced only when burnt out.
Have 6xTek T5.
My tank has almost non existent algae.
My SPS have VERY nice color and growth I have Pink, bright green, blue tip Dual Color SPS and green tip as well.
So go figure.

Low bio load (only 3 fish in 65 gal tank ), high ORP (with high air flow) air driven skimmer it is constant just over 450. Second skimmer is Deltek 600 HOB.

[mark]

Is it shift in temperature, 14K to 10K, don't see a problem as lots start with 10K bulbs, or they basically stay at 14K but with just a increased narrow spike at a lower wavelength.

(or just a conspiracy by the manufactures and supplier to replace our bulbs)

[daniella3d]

In deed. I have a fugi purple that is very red on my other tank and no algae grow. I used to have PC that were near a year old and no algae either.

I use GFO in both my aquarium + micro algae and not overcrawding and that does the trick.

We must not forget that zooxanthellae are algae and that coral need them to grown, at least for photosynthetic coral.

The spectrum and intensity does change in various lighting bulbs but its not the major causes of an algae bloom. Algae will grow because there is an access of nutrients. You could put a ton of red over a tank will low nutrients and no algae will grow. In fact that’s what people are doing with the new fiji purple and ati purple plus bulbs, they are adding red spectrum. If you have excess algae growth you will have access nutrients (nitrates, phosphates, silica, etc). However, the added red and yellow spectrum will make a high nutrient tank grow algae much faster because algae use red spectrum very well for photosynthesis.

[wickedfrags]

No significant correlation between bulb age (or spectrum) and algae growth in my experience. Water quality (nutrient levels) dictates algae growth, not quantity or spectrum of light.

I understand that older bulb lose intensity and there's a slight spectrum change. I've heard that old MH bulbs can be a contributing factor to unwanted algae growth. Could someone explain the theory behind algae growth?

[Myka]

If everything else is in order, the bulb age and spectrum will have no effect on algae. On a tank that already has an algae issue a change in bulbs and/or spectrum can really help. On a tank on the brink of an algae bloom aging bulbs can be the straw that broke the camel's back.

My tank is a very good example right now. One of my 20K halides burned out. I only have 10K as spares. So my reef has a 10K on the left side (with 6 months use on it) and a 20K on the right side (with 14 months use on it). On the left side a minor dusting of diatoms shows up in late afternoon under the 10K bulb, but not on the right under the 20K bulb. Also, you can see a difference that there is more to scrape off the front glass on the left than the right.

[chris88]

The shift in spectrum isn't the issue with old bulbs, it's the major drop in par. Its on average about a 30% drop in par after 6 months and sometimes a 50% drop after a year. This happens with t5's or halides. This isn't a debatable issue. There is a lot of data on the decrease in par so its a fact and not a conspiracy. I would not suggest running any type of bulb for longer then a year unless you are doing a fowlr tank. I change my t5's at about 9-10 months.

[Myka]

The shift in spectrum isn't the issue with old bulbs, it's the major drop in par. Its on average about a 30% drop in par after 6 months and sometimes a 50% drop after a year. This happens with t5's or halides. This isn't a debatable issue. There is a lot of data on the decrease in par so its a fact and not a conspiracy. I would not suggest running any type of bulb for longer then a year unless you are doing a fowlr tank. I change my t5's at about 9-10 months.

It is a debatable issue because your numbers aren't right, but that's a different topic. Please explain how lower PAR affects algae growth...?

[chris88]

My numbers are close to right on, but it does change depending on the type of bulb and cooling of the bulbs. Just check reef central there are numerous threads on par decrease over time. I guarantee you my numbers are on par with what everyone has been testing and coming up with.

I didn’t make any mention of how par effects algae growth. My comment was directed to the people who said there was no need to change their bulbs unless they burn out. I already address effects color spectrum has on algae growth in my previous posts.