I did this experiment for the El Natural section, but I figured some of you might want to see it too.
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 if I only had 11.7W of light, rather than the 30W I have.
Anyway, back to my side of the fourm.
Whiskey
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Linear Mode
