# Light Temp. effect on algae growth



## OperJeff (Apr 14, 2007)

I had started this topic in the thread about using willow branches in water to control green water. and so I am giving this topic its own thread as not to take away from the previous.

the reason for starting this experiment is because I noticed that I could only produce green water under a certain light temp. so we decided to test it...

I started with the following

the constants were -
2, 5 gallon buckets of water - water was fresh from tap, dechlorinated NOT cycled
each with 1 feeder goldfish in it. 
everyday i fed the fish equal amounts
equal aeration in each bucket
equal light duration
equal light reflector
no mechanical filtration
no water changes performed or any added since

the variables were 
bucket A
27 watts 
1300 Lumens 
cool bulb "day light"

bucket B
23 watts
1600 Lumens
warm bulb "soft white"

its been close to 3 weeks now and here are the following results
bucket A is on the Left



water details



The results are opposite of what I experienced previously. from my experience I had always ended up with algae blooms under the warm temp bulb, but in a controlled test like this the cooler temp light on Bucket A prouced green water one week earlier. Bucket B produced some hair algae and what looked llike the start of an algae bloom but none of them survived past 3 or 4 days.


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## mikenas102 (Feb 8, 2006)

Do you have an actual Kelvin rating for the bulbs besides "daylight" and "soft white"?


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## OperJeff (Apr 14, 2007)

the lights are from N.Vision, and I wasnt able to get a Kelvin rating from them. but using this chart

http://www.1000bulbs.com/pg/Color-Measurement/

from a website which sells the same bulbs

would put the light for Bucket A @ 5600k
and 2700-3000k for Bucket B


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## mikenas102 (Feb 8, 2006)

Perhaps bucket B didn't grow as much algae because such a low Kelvin range isn't really good at growing plants. In aquarium use that bulb wouldn't do too well for you if it is in fact 2700-3000k.


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## MatPat (Mar 22, 2004)

Nice job on the experiment but I think you would get more accurate results if you were to use bulbs with the same wattage. 

Bucket A had 5.4 wpg while Bucket B only had 4.6 wpg. While an extra 4 watts might seem insignificant for our tanks, that extra 4 watts (almost 1wpg for the bucket size) probably made a significant difference in this experiment even thought the lumens per watt are relatively similar. Look what adding an extra watt per gallon does for growth (both plant and algae) in an aquarium.

Color spectrum of the bulbs (i.e. blue and red output) may have had an impact also since plants need the red and blue spectrum for photosynthesis.


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## OperJeff (Apr 14, 2007)

I found that the bulb temp for Bucket B was 3600k, which was printed on the ballast of a bulb of the same color rating from the same company.

Id have to agree with MatPat, my only ideas as to why Bucket B didnt grow algae is that the 3600k bulb doesnt go far enough into to the blue and red spectrums so its kind of like in "no-mans" land of photosynthesis. 

I think a better experiment would be to focus on which light spectrum ("blue vs red") does green water thrive on. since light temp is very broad.


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