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Re: Cloudy by day crystal clear by night

on 01:48 PM 8/26/99 , Richard Sexton wrote:

 >I have a 40G tank with a bunch of plants and a large cology
 >of Endlers that goes cloudy at night then clears up
 >every day so that by about afternoon it's crystal clear
 >again. Has anybody ever seen anything like that?

I've seen it every day for the last month or so in my 29G, and nearly 
eliminated it. Not sure about your cloudiness, but mine is definitely green 
water algae. Doesn't look green until I siphon it into a white bucket (!) 

After working on the nutrient problems that caused most of the other 
algaes, this one kept getting worse. My theory is that it was caused by 
ambient light. I keep my tanks on a late cycle, about noon to midnight, to 
match my sleep schedule so I can see the fish. During the hours before 
noon, filtered sunlight comes in and adds a bit of light; additionally, the 
room lights were often on before or after the photoperiod.

I think the green water algae grows in this low light, while the regular 
plants are still "asleep". When this problem was at its worst, the tank was 
nitrate-limited and had an excess of phosphates. When the tank lights 
turned on, I assume the higher plants (and higher alga) out-competed the 
unicellular algae for phosphates, clearing the water.

This relates to the recent posts about green water and Calcium. For my 
theory to hold, the entire colony of unicellular algae must die of 
malnutrition within the space of a few hours. Perhaps this is possible. 
There may also be a consumer that overcomes the algae after its growth 

To combat this, I have been leaving room lights off as often as possible, 
and shifted the photoperiod closer to the real day/night cycle. Now I just 
have a slight cloudiness in the morning, and it's usually gone by 3 or 4 pm.

On the other hand, I've also been adding KNO3 recently to combat the excess 
of phosphates, and switched to TMG from Flourish. So other factors are 
probably involved.

michael moncur   mgm at starlingtech_com   http://www.starlingtech.com/
"An ignorant person is one who doesn't know what you have just found out."
                 -- Will Rogers