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re: PMDD Advice Request

>Tank size and light level: 75G: 4-55W AH supply PC
>bulbs, 10G: 2-20W fluorescent tubes (shop light
>Duration of the light: 75G: 10.5 hours, 10G: Close to
>15 hours
>(Virtually no problem here with algae except for the
>spot algae that my Pleco loves to eat.)

Your lighting at 2.93W/gal for the 75gal and 4w/gal
for the 10gal, you have a good amount of light.  I
would reduce the duration of light on the 10 gal to
10-12 hrs/day, this may get rid of the green spot
algae you see.

<<Water quality report data:
Nitrate:        1.6 mg/l
Phosphate: n/a (Other parts of the city report 0.8 to
Hardness:    130 mg/l
pH:              8.4 (7.2)
Calcium:      38 mg/l
Magnesium: 7.8 mg/l
Chloride:     3.6 mg/l
Iron:            0.1 mg/l (0.01)
Sodium:       2.3 mg/l
Zinc:            0.01 mg/l
Manganese: 0.01 mg/l (0.001)
Sulfate:        28 mg/l

Note:   These figures are maximum level for 1999. The
city water authority measures only three parameters
daily and the daily averages for these are listed in
the parenthesis.>>

You really need to measure these parameters in your
tank to see if your plants need more nutrients.

The nitrate levels (1.6 mg/L) look good.  You may wish
to add KNO3 to bring this up to 5 mg/L (ppm).  You
should shoot for 0.1 mg/L iron.  Your pH will come
down with CO2 addition.  You should measure your KH
and pH so that you can use these data to calculate
your CO2 concentration (www.thekrib.com/plants).

<<I have some staghorn algae growing in 75G tank (and
getting worse
lately). I know black brush algae are still hiding in
the dark corners on
old leaves and stray roots. But my trusty algae
busting crew (a few SAE,
oto, FFF, pleco, platies) plus occasional hand removal
are generally keeping
them in check.>>

The presence of staghorn and black brush algae
suggests that your phosphate levels may be high.  One
should shoot for 0.2-0.5 ppm.  Or recently on the APD
there is a discussion that keeping a 16:1 ratio of
nitrates to phosphates is also a good way to keep
algae in check.  Check it out.

See Chuck's site at
and the Krib at
for good info on using a nutrient balance to keep
algae growth under control.

Good luck,

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