XJfella95

I read some where that blue light, particularly in the 450nm wave range shuts down photosynthesis and also breaks iron down in the water column to a chillated version ready for plants.

Waldstadt states that to battle algae one must make iron the limiting factor.

Does anyone have any experience with turning off their moon lights and having algae disappear? What is the general consensus with this theory?

gr33nthumb

Well I cant tell you about that particular wave length, but I do have a similar experience. I purchased a used 150w metal halide and it came with a 14000k lamp so i used it. Within 1 photo period (8hours) I could watch the algae grow. Green water and a few others where extremely prevalent. That is just my experience!

XJfella95

When you installed the new metal halide did it match previous light intensities? If not did you up the fert doses?

I'm curious because I run a single 3w royal blue LED as moon light and seem to have more algae issues than before.

gr33nthumb

Sorry I'm a little late! I honestly do not know about the intensity change as I went from 14000k to 6700k, very different outputs. After the swap I kept the dry fert dosing the same along with Co2 and the algae backed off within a couple days and plant growth was phenomenal. I almost want to set a test tank up to mess with blue light and algae. I have no scientific perspective but there seems to be a correlation between the two. What wavelength is your moonlight LED?

Newt

A university study (I forget which one: from an article in the Journal of Plant Phisiology) found evidence that some plants are affected by light at around 460nm and photosynthesis does not take place and that far red (infra-red > beyond 700nm) does shutdown photosynthesis.

In Diana Walstad's book she states heavy amounts of light in the blue area of the spectrum will breakdown the iron's chealant (photo-reduction of iron) leaving the iron in a 'free' state which allows algae to easily feed on it.

XJfella95

Yes, that's exactly what I'm talking about. I tried to be as ambiguous with my question as possible because I was curious to see if anyone else has had experience with a blue light and algae growth.

I have a slight hair algae problem in my nano and was curious I'd it could be coming from my single, Royal Blue CREE XP-G led, that I use as a moon light.

I noticed that quite often after I

I'll have to run my moon light on a separate timer rather than the day/night cycles that my Zoo-med digital outlet strip let's me. This way ill be able to provide a dark period and not have the blue on 14hrs a day

I read elsewhere that a few people use cool white LED's to mimic moon light better. I like this idea and plan to go down that road once I figure out a good way to mount a DIM4 controller in a project box or how I can make a hood that has the controller built in. Until then I'll stick with my RB LED and a moonlight driver.

AaronT

The iron that is broken down should be quickly taken up by the plants.

Excess organics are a much bigger culprit for algae growth. Keep your tank water clean, very clean. Regularly do large water changes, remove dead leaves, mulm build up on the substrate, service the filter, etc.

gr33nthumb

that is some awesome information from all those posts, fascinating stuff especially about the state of iron in relation to light. Seems to be the opposite effect with 14000k in a planted tank, as all the spectral graphs for that color temp I can find show a huge spike at 450-460nm. It must be that most plants cant use that, yet algae adapts quick and easy, hence thriving over the plants. Interesting....

The Trigger

Yeah I believe those bulbs and spectrums are made to be used mainly on reef tanks. Those wavelengths are best utilized by corals and such. I've heard so many horror stories of people using the actinic bulbs and bulbs above 10,000k and having nothing but algae problems.

Newt

I thought these graphs would help you>

As you can see in the gif below photosynthesis drops off at ~460nm. Why use 460nm actinic bulbs?


This is the scale of light humans can see. Approx 400nanometers (nm) to 700nm.
Its a scale in wavelengths of light (electromagnetic energy).


Here is the kelvin (K) line drawn on a chromiticity map of all the colors:


This is the color representation of the kelvin temperature scale. It is taken from the black line on the gif above. Do not confuse this with nanometers in the visible spectrum of colors (a wave length of light). The kelvin color is derived by the temperature of a black body (iron) being heated. It starts at red to orange to yellow ---colder to warmer---to white to blue to lavendar to purple.


I think its more about the light on the nanometer scale and not the kelvin color temp of a bulb that causes issues. I still use GroLux WS and GroLux Standard bulbs for dawn/dusk lighting and to hi-lite the color of my Cardinals. The WS is 3400K and the Std is not given but based on the color the bulb burns I'd have to guess 18,000 to 22,000K as it is lavendar/purple. I dont have algae issues other than a light amount of GSA on slow growers and minimal GDA on the glass that I scrape about every 2 weeks.
This is a gif of the light in the visible spectrum the GroLux Std puts out: