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Re: Nitrates/green water/test kits (question)

I recently went through the same thing with persistent green water, couldn't
get rid of it for months!

> I am guessing that the outgassing of CO2 due the HOT Magnum caused a pH
> change and the angels are in shock.  Does anyone know how long this lasts
> and if they will recover (previous pH was about 6.8).  The rest of the fish
> seem fine.

Agreed. I had the same problem while running a HOT Magnum. To remedy this, I
discontinued CO2 injection until the water was clear.
> The plant growth and health has continued to increase since the first KNO3
> addition.  The green water is returning - it is now 24 hours after running
> the HOT Magnum and the green water is at the misty-hazy water stage but I
> imagine in a couple of days it will become completely green.  I have had a
> history of green water problems.  In my last tank I after four months I
> finally gave up and got rid of the tank.  I tried everything, water changes,
> turning off the lights for days, and nutrient control.  Even on that tank I
> remember struggling to provide enough NO3 - because the test kit told me
> there was very little.

IME, micron filtration with a HOT Magnum will not completely filter out all
of the suspended algae. I had to add a flocculent to get the water
completely clear. No adverse affects on the fish. I also have persistent low
nitrate levels. I dose KNO3 on a weekly basis, or as needed to maintain
aprox. 5ppm.
> With the lack of reliance on test results I am unsure how much KNO3 to add
> on a regular basis.  If add too much on a daily basis I could reach toxic
> levels of 30ppm within 2-3 weeks.  However, if I stand on the side of
> caution I could have a nitrate deficiency within days.  In the last week I
> have added about 15ppm NO3 to the water column.  I may be able to use the
> test kit to determine if NO3 is over 12 ppm but I guess not much else.

I used to think along the same lines as you do. The "optimum" level varies
from tank to tank. In my tanks, as long as there is some in there, I'm ok.
If I test and I got 3ppm, I won't dose.

> My next approach will be to cover the surface with duckweed.  If that doesn'
> t work I will get all the fish out, put some kind of netting around the
> filter intake and put loads of daphnia in.  Does anyone know if either of
> these approaches is effective for green water?  It seems whatever I do it
> just comes back.  According the test kit there are undetectable phosphates
> in the water column.  If the test kit is correct then what are the algae
> living (in fact thriving on).  I don't have any problems with any other type
> of algae - apart from some green spot.  Anyone know of any other tricks?.

Here is what worked for me:
1) Shut off the CO2
2) Micron filtration (HOT Magnum) with a flocculent added to the water.
3) Leave off the lights while micron filtering
4) When the water is clear (remove magnum), resume CO2, DO NOT add any
fertilizers, and slowly work the light duration up to 10-12 hours a day.
Start with 6 hours for a week, then 8 hours for another week etc.

I hope some of this is helpful. Feel free to email me off list if you would
like more information of how I won my war with green water.

Phil Behrends
Colorado Springs, CO