# [Wet Thumb Forum]-A experment to answer my question and maybe yours.



## whiskey (Oct 9, 2004)

In an attempt to fix some major problems with my SPS tank, I bought a LUX meater.

I have always wondered how much the yellowed water (due to tannans) effected the light penetration to the bottom of the tank. Here is an experement I plan to do to find out.

Subject: 10 gallon tank that has not had a water change for 4 months, the water is noteably yellowed. Plants are healthy and growing, and algae is not a problem. This tank is set up "by the book" with no co2, water changes, or ferts other then potting soil.

Lighting: 2 T8 NO 15W tubes 5 inches off the water for emergant growth, bulbs are 7 months old.

Water movement: 1 aquaclear "mini" HOB powerfilter.

Experiment proceadure: I will clear off all the duckweed on the top of the tank, and ensure the tank is topped off to maintain the same water level. I will then place the light probe at the bottom centre of the tank and measure the amount of light reaching the bottom of the tank, I will trim any plants that may shadow the probe. I will take pictures.

I will then leave the probe in place (not move it) and change aproximatally 25% of the water and retake my reading. Then I will change another 25% of the water and retake my reading. Finally I will drain the tank as low as possible and refill it compleatly and take my final reading.

By compairing these readings we can see how much (% of total) yellowed water effects light penetration.

Is there anything else you would like me to do while performing this experiment? Would you like me to use a diffrent procedure? Something more scientific? Do you want to see the results, or does nobody really care







.

Thanks,
Whiskey


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## DataGuru (Mar 11, 2005)

That sounds like a great plan to me.









Can't wait to see the results!


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## JERP (Feb 4, 2003)

Sounds like a good idea. I would give the tank 1 day between water changes and taking your measurement so debris is not interfering.

For grins, you might consider taking a few measurements at various depths and with the light at various distances from the surfaces of the water. repeating the depth experiment with a deeper tank might be interesting too. An inverse square relation is normally expected with moving the sensor away from the light source, however, this wont occur in an aquarium to to refraction off the tank sides. At a certain depth, you stop losing light out of the sides and the light reflects off the sides and back into the tank. After this depth, you should notice that light intensity does not drop nearly as quickly.


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## whiskey (Oct 9, 2004)

> Originally posted by Betty:
> That sounds like a great plan to me.
> 
> 
> ...


I will conduct the experiment tonight, I hope.

Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by JERP:
> Sounds like a good idea. I would give the tank 1 day between water changes and taking your measurement so debris is not interfering.


I am going to be really carefull refilling the tank to make sure nothing gets kicked up. The reason I don't want to wait a day is it would force me to move the probe, and possible alow for some yellowing to build back up. I will fill the tank on a diffusion cup to allow as little kickup as possible.



> For grins, you might consider taking a few measurements at various depths and with the light at various distances from the surfaces of the water. repeating the depth experiment with a deeper tank might be interesting too. An inverse square relation is normally expected with moving the sensor away from the light source, however, this wont occur in an aquarium to to refraction off the tank sides. At a certain depth, you stop losing light out of the sides and the light reflects off the sides and back into the tank. After this depth, you should notice that light intensity does not drop nearly as quickly.


I did plan to do that after the aquariam was refilled and the water clear, for my own records, (monitor bulb output over time) but I could post that here too. Did you want me to do it before? I don't want to make changes to the probe during the experiment so it will have to be one or the other.

Thanks,
Whiskey


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## whiskey (Oct 9, 2004)

Here it is,...

Introduction:
The purpose of this experiment is to determine how much water turbidity or yellowing effects light penetration to the bottom of a standard 10-gallon tank.

Hypothesis:
I believe that yellowing or turbidity of the water due to release of tannic acid and fish feices and food significantly affects lights ability to penetrate through the water or freshwater plants live in.

Equipment:
10-gallon tank explained further under the subject heading

Python no spill drain and fill water-changing device to allow changing of the aquarium's water without touching the aquarium itself, all draining and filling can be done remotely.

Milwaukee SM700 LUX light meter with submersible light probe, used in the X10 resolution allowing a resolution of +-10LUX, and an accuracy of +-6% reading in +-1 digits. All measurements done in LUX, and converted to PAR for further comparisons. Par conversions done using the 74units LUX =1unit PAR for florescent tubes.

Tap water for water changes, unfiltered however I did use a standard hobby decloranator product to remove potentially harmful chlorine. This was dosed at a rate of 1 ml per 10 gallons of water changed.

Diffusion cup to prevent stirring of the soil during refilling.

Camera for photos Kodak CX6230 easy share

Subject:
10-gallon tank

The bottom of the tank is layered with 1 inch Hypotnex potting soil, and 1 inch of inert pea gravel 2-4MM in diameter. There are 4 pieces of petrified wood as decoration.

Due to the space the gravel/soil/decorations take up, I estimate the actual water volume to be aprox 8 gallons using the volume calculator on RC, keep in mind I will use 8 gallons as tank volume for all further calculations.

The tank is filtered by an aquaclear "mini" using a standard sponge cartridge; it contains no carbon, and no bio-media or other additives. This filter will be shut down for the testing to avoid potential test altering ripples in the water.

This tank is lit by 2, 18" T8 bulbs, they are 9 months old and I have had them on for at least ½ hour before testing began to ensure they are warmed up and their intensity does not change throughout the experiment.

The water in this tank has not been changed for 4 months and is noticeably turbid/yellow assumed to be caused by release from the soil of tannic acid, and rotting feices, and food.

Picture:









Procedure:
First I remove all duckweed from the surface of the aquarium and shut off the filter to avoid these things affecting my results.

Then I position the python no spill drain and fill in it's place on the far left of the aquarium and the light probe resting on the bottom of the tank dead centre, in the gravel, then I put the hood back on as best as possible. Nothing in the aquarium will be touched by me from this point forward; all water changes are done from the sink to avoid human interference with the readings.

Now I measure the aquarium, from the point the gravel stops to the current water level. I mark the tank at 25% of that for use in my first 2 water changes. Keep in mind this mark is at 2 gallons, because I am only taking into account the part of the aquarium that is not covered by gravel or soil. I also mark the current water level so I may fill the tank up to that point when refilling.

Picture of setup pre experimenting:








Picture of light probe









---Before the first reading was taken it was necessary to reposition the Python tube and change the diffuser due to the fact that it would not stay put. You will see this change in the next picture.

I now take my first base line reading from the light meter this is how much light is getting to the bottom of the tank with the water in it's current state.

Reading=510 LUX or 6.89 PAR

Now I drain the tank to my 25% mark, and carefully refill it to avoid stirring up any soil, this is where the diffusion cup comes in handy. When I refill the tank, I do it to my full tank line. This is a water change of 25% or 2 gallons. I then let the new water settle for a moment and take my picture, and reading.

Picture:








I now take another reading

Reading=610 LUX or 8.24 PAR

Now I do a second 25% water change using the same method as before, now remember that only 75% of the water (6 gallons) is old water, and 25% (2 gallons) is freshly added water. This means when I do a second water change of 2 gallons I am removing 11/2 gallons of old water and 0.5 gallons of freshly added water, so this means at the end of this water change I have changed out 3.5 gallons of old water (0.438%) NOT 4 gallons (50%).

Picture:








I now take another reading from the light meter.

Reading =700LUX or 9.46 PAR

For the final water change I remove all the water possible, to get as close to a 100% water change as possible. I estimate that I have removed 96% of the water contained within the tank, and refill the tank especially carefully to avoid stirring the soil. The tank is then filled and the water aloud to settle and another reading taken.

Picture: of water drained as far as possible









Picture after refilling









Final reading = 1290 LUX or 17.43 PAR

Conclusion:
For anyone who actually read this whole thing, here are my conclusions. From the first reading to my last I got a 252.94% increase in light (first reading was 39.53% of the last one) making it to the bottom of the aquarium simply by clearing up the water. I believe based on these numbers this proves my hypothesis that water turbidity plays a major role in light penetration through the water; furthermore I believe that if the aquarist wishes to get the most out of his lighting setup it is very important that the water be as clear as possible. By these numbers, on the bottom of my tank, if I had kept the water clear, I would have the same amount of light reach the bottom of the tank if I only had 11.7W of light, rather than the 30W I have.

*This post was edited by me to clear up a mathimatical error, I was tired, sorry for the confusion*

Thanks,
Whiskey


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## littleguy (Jan 6, 2005)

Really REALLY cool. This kind of thing is what makes this forum so great. Long live the experimentalist approach!


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## imported_Winzzy (Jun 25, 2003)

WOW!


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## littleguy (Jan 6, 2005)

This may actually be one of the best reasons TO change the water in natural aquariums. i.e. even if ammonia, nitrates, etc. are negligible, and all the water parameters are good, a water change may still be necessary for returning lighting to full strength.


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## littleguy (Jan 6, 2005)

If we assume that materials dissolved into the water at a uniform rate, we can estimate the decline in lighting intensity over the past 4 months. Pretty cool.


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## DataGuru (Mar 11, 2005)

Very nice! That's quite a difference.


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## imported_BSS (Apr 14, 2004)

Now, that's good stuff!! (And before I get another snide comment about a high light guy coming over to the dark side (pun intended), this really isn't just an El Natural topic IMO







).

One question. So, why is it just a 39% increase in light penetration? Likely something I don't understand about light intensity. But if you go from 510 LUX up to 1290 LUX, that seems close to a 3x improvement, so why isn't it greater than 39%? The mathematical side of me is confused!

Great data, Whiskey!
Brian.


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## dwalstad (Apr 14, 2006)

Thank you for doing this experiment.

Folks, I would take care about making blanket statments that water changes help maximize lighting

Whiskey, your starting tank water is dim and brown-colored, indeed. Tannic acids will absorb a fair amount of light--- as you have shown. Any time you see color in the water, you can assume significant light absorption. If I had a tank with the brownish color you have shown, I would probably (for the plants and aesthetic reasons) do a water change and/or add charcoal to the filter.

Brown-colored water is usually a temporary phenomenon. As the soil "settles down", the leaching of tannic acids should dimminish.

I don't have tannic acid-stained water in my tanks, despite going for 4 or more months without water changes. To my eye, the water is crystal clear without any coloration. If the water is crystal clear and colorless, the light reduction will be insignificant-- probably not worth a water change.

Wetzel's Limnology textbook has some data on this (comparing light absorbtion by distilled water v. various lake and river waters). I'll try to dig it out at some point.


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## littleguy (Jan 6, 2005)

> Originally posted by Diana Walstad:
> Folks, I would take care about making blanket statments that water changes help maximize lighting


Oops let me rephrase. In an earlier post I asked what prompts people to finally make a water change in a low-tech tank. Some people said hardwater nutrient deficiencies, some said aesthetics, some said guilt







.

This experiment suggests another valid reason for someone to change the water in a low-tech tank. But only if the water is noticable darkened/turbid AND more lighting is needed for some reason.


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## whiskey (Oct 9, 2004)

> Originally posted by Diana Walstad:
> Thank you for doing this experiment.
> 
> Folks, I would take care about making blanket statments that water changes help maximize lighting
> ...


I agree, if the water is clear then this is probably no light loss, but that is not what I was looking to prove.


> Originally posted by Whiskey:
> Hypothesis:
> I believe that yellowing or turbidity of the water due to release of tannic acid and fish feices and food significantly affects lights ability to penetrate through the water or freshwater plants live in.





> Originally posted by Diana Walstad:
> Brown-colored water is usually a temporary phenomenon. As the soil "settles down", the leaching of tannic acids should dimminish.


This is true, and I have seen this in my year+ old tanks, however I tore all those down to start my 180 so currently have none of those to test







.


> I don't have tannic acid-stained water in my tanks, despite going for 4 or more months without water changes. To my eye, the water is crystal clear without any coloration. If the water is crystal clear and colorless, the light reduction will be insignificant-- probably not worth a water change.


When some of my tanks get a little older I will redue this experiment but that won't be for a while, I expect this second experiment would prove what you are saying.


> Wetzel's Limnology textbook has some data on this (comparing light absorbtion by distilled water v. various lake and river waters). I'll try to dig it out at some point.


I look forward to this data, it would make for a good read.

Thanks,
Whiskey

Edited for grammer


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## whiskey (Oct 9, 2004)

> Originally posted by littleguy:
> Really REALLY cool. This kind of thing is what makes this forum so great. Long live the experimentalist approach!


Thanks,it was fun.
Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by The Winzman:
> WOW!












Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by littleguy:
> This may actually be one of the best reasons TO change the water in natural aquariums. i.e. even if ammonia, nitrates, etc. are negligible, and all the water parameters are good, a water change may still be necessary for returning lighting to full strength.


If the water is discolored then I agree compleatly. If you can see discoloration then it is probably effecting your light penatration regardless of test results.

Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by littleguy:
> If we assume that materials dissolved into the water at a uniform rate, we can estimate the decline in lighting intensity over the past 4 months. Pretty cool.


But that graph would only be accurate for my tank, over those 4 months, as time goes on less tannins are releaced and diffrent soils releace tannins diffrently so we can only graph what did hapen, not what will happen







.

Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by Betty:
> Very nice! That's quite a difference.


Thank-you I love playing with my toys.
Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by BSS:
> Now, that's good stuff!!


Thanks


> (And before I get another snide comment about a high light guy coming over to the dark side (pun intended), this really isn't just an El Natural topic IMO
> 
> 
> 
> ...


Just messing with you mate,... no offence ment. In fact I think this applys more to you then me, you have more light to loose







.


> One question. So, why is it just a 39% increase in light penetration? Likely something I don't understand about light intensity. But if you go from 510 LUX up to 1290 LUX, that seems close to a 3x improvement, so why isn't it greater than 39%? The mathematical side of me is confused!
> 
> Great data, Whiskey!
> Brian.


Percent works like this, IF I assume that 1290 LUX is 100% Then I can say that 510 is 39.53% of it,.. Oh damn, you are right it is a * increace of 252.94% if we start from 510* I was *getting 39.53% of the last reading in the first reading*, We can also say that I was loosing 60.57% of the total (assumed to be 1290) to the murky water.

sorry, I was tired when I typed up the math bit.

Good catch,
Thanks,
Whiskey


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## Miss Fishy (May 13, 2006)

Great experiment, Whiskey! I was surprised that there was such an increase in light once the water was clear. It makes me wonder what would happen to plant growth rates if I added some charcoal to one of my tanks which has yellow/brown water (although it may not make much difference to this tank since it gets a lot of sunlight). 

From Alex.


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## DataGuru (Mar 11, 2005)

allright... we started with 510 lux and ended with 1290 lux.

There's two ways to look at the difference.

We can take the difference between the two and divide it by the first reading. That's 780/510 or 1.5 times more light.

or we can do a ratio. endingLux/startingLux 1290/510 or 2.5 times more light.

So how'd you get the 39.53% increase?


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## whiskey (Oct 9, 2004)

> Originally posted by Betty:
> allright... we started with 510 lux and ended with 1290 lux.
> 
> There's two ways to look at the difference.
> ...


I didn't, sorry I was tired and typed wrong, in the first reading I was getting 39.53% of the last reading. If we start from 510 LUX then the reading of 1290 is 252.94% higher.
Sorry for the confusion,
Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by Miss Fishy:
> Great experiment, Whiskey! I was surprised that there was such an increase in light once the water was clear. It makes me wonder what would happen to plant growth rates if I added some charcoal to one of my tanks which has yellow/brown water (although it may not make much difference to this tank since it gets a lot of sunlight).
> 
> From Alex.


I was also quite supprised,I have added carbon to that tank so I can keep using my light. I am not sure if it works the same with sunlight, because that is quite a powerfull light source, but it is worth a shot.

Thanks,
Whiskey


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## whiskey (Oct 9, 2004)

You guys have brought up another good point, because of my math error, I caculated the light compairison wrong two. This is the correction.

If I had kept my water clear, I would have the same amount of light on the bottom of my tank if I had been using a 11.7W light!!!!! This means I was waisting 18.3W of power to the water.

Whiskey


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## whiskey (Oct 9, 2004)

*I edited the experiment post to clear up the mathimatical error, sorry for the confusion*.

Whiskey


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## imported_BSS (Apr 14, 2004)

> Originally posted by Whiskey:
> Just messing with you mate,... no offence ment.


No offense taken!! I just couldn't pass on the opportunity to try to dish some of it back out







.


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## dwalstad (Apr 14, 2006)

> Originally posted by Whiskey:
> *I edited the experiment post to clear up the mathimatical error, sorry for the confusion*.
> 
> Whiskey


Thanks Whiskey for doing this experiment and giving us some real numbers to work with. I've seen tanks worse than this (the only plants growing are, not surprisingly, java fern). I knew that the tannins reduced the lighting, but not how much. Now we have some idea.

A 60% light reduction due to yellowish water is substantial. It certainly could inhibit plant growth.

Good work!


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## whiskey (Oct 9, 2004)

> Originally posted by BSS:
> 
> 
> > quote:Originally posted by Whiskey:
> ...


Nice,... So, how clear is your water?

Whiskey


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## whiskey (Oct 9, 2004)

> Originally posted by Diana Walstad:
> 
> 
> > quote:Originally posted by Whiskey:
> ...


Thanks, I always kind-of wondered if I worried about water clarity too much, especially in the 24 inch deep 180, so when I got this light meater this experiment jumped right to mind. I think that it would be prudent to run charcoal in the filter of newly established tanks to avoid this problem. The charcoal could be removed sometime down the line (month or two depending on your soil) especially because it is really important in new tanks to have vigarious plant growth to avoid algae.

I am glad my little experiment could be of some use.

Thanks,
Whiskey
Whiskey


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## flagg (Nov 29, 2004)

Wow! Great experiment Whiskey! Reading your results took me back to my old days of high school science experiments. I was surprised to see just how much light is absorbed by the tannins in the tank. I know wonder how it is that I my old tank flourished w/ live plants and brown water from the added "Blackwater Extract" by Kent....

-ricardo


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## flagg (Nov 29, 2004)

Hey Whiskey, you know what I'd like to know? How much do floating plants affect light penetration? I mean, clearly, having the surface covered w/ duckweed or salvinia or water lettuce is going to reduce the light that reaches the bottom of the tank, but by just how much exactly? If you ever get the opportunity, perhaps you could test that out for us....

-ricardo


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## whiskey (Oct 9, 2004)

> Originally posted by Ricardo V.:
> Hey Whiskey, you know what I'd like to know? How much do floating plants affect light penetration? I mean, clearly, having the surface covered w/ duckweed or salvinia or water lettuce is going to reduce the light that reaches the bottom of the tank, but by just how much exactly? If you ever get the opportunity, perhaps you could test that out for us....
> 
> -ricardo


A lot







, when my tank gets recoverd with duckweed I will give it a test, it will take a while though.

Whiskey


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## flagg (Nov 29, 2004)

Sounds good to me! You know, Whiskey, the more I think about it, the more I wish I too had one of these water proof light meters. Like, I would like to know just how much more light my tank receives with the flo. light on when it's bathed in sunlight. The sunlight is so bright you can't tell if the light's on or off except that when it's off, there's a slight reduction in the light in the tank. A noticeable reduction, but not by much....

-ricardo


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## Jane of Upton (Jul 28, 2005)

Wow, Whiskey - EXCELLENT Experiment!

I'm also surprised at how significant the light reduction is! 

That submersible light meter is cool..... as I was reading this thread, I kept wondering "how is Whiskey getting the light meter into the water? Is it in a plastic bag, and wouldnt' that affect the experiment?"...... Ha! Then I saw that you have a waterproof one..... VERY cool toy! I didn't even know there WAS a waterproof one! 

What a great thread! Thanks for conducting this experiment!
-Jane


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