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-   -   clean water and green algae?? (

conger 11-23-2008 08:50 PM

clean water and green algae??
Hi all, sorry in advance for the long post, but I wanted to give as much info as I could up-front.
I hope this doesn't discourage people from reading it!! I've got some serious green algae (not
hair) growing in my tank, and until now I've just chalked it up to one of the algae phases a new
tank goes through. However, it's been persistent for about a month now, and doesn't show any
signs of decreasing. I test my water thoroughly, and it appears to be very good quality (params
below). So why won't this algae go away? Any ideas on what specific type of algae this is, and
what I might be able to do to reduce it?

I'll give a thorough description of the tank's equipment, history, and current water parameters here:

The tank has been up and running for about 4 months now. 90 gallon FOWLR (and a colony of
zoas), w/ 30 gallon sump divided into skimmer, refug w/ cheato and 18W light on opposite phase
from display, and return pump chambers. Skimmer is an Octopus NW 150. Coralife 18W UV unit.
I've got two Koralia 4 powerheads in the display. Coralife Lunar Aqualight light fixture, CF w/ four
65W bulbs (two 10000K, two actinics)... actinics on from noon-midnight, daylights on from
3PM-9PM (lunar LEDs on midnight-noon). About 140 lbs rock (70 lbs actual liverock from LFS, 70
lbs base rock). Currently have a 4" sandbed, but this is recent... had only a 1" sandbed for the first
three months, and padded it up to 4" about a month ago (the green algae was there before I did
that to the sandbed). I perform a 25 gallon water change every two weeks. I supplment with:
B-Ionic, Kent Marine Tech-M (magnesium), Kent Marine Liquid Calcium. I use home-made RO water,
and use Reef Crystals salt mix, and 34 gallon Brute trashcans to mix the water and store the RO for

Current water parameters are (liquid API test kit):
sg: 1.023
pH: 8.2
Ammonia/Nitrites: 0
Nitrates: 5 ppm
Phosphates: undetectable
Alk: 12 dKH
Calcium: 380
Magnesium: 1320
temp: 78 F

Current tank inhabitants are:
1 midas blenny
1 4-stripe damsel
1 firefish goby
1 royal gramma
4 turbo snails
8 small hermit crabs
1 coral banded shrimp
6 jumbo nassarius snails
10 bumblebee snails

The algae that is growing is definitely not hair algae... it's also not green coralline, as it comes
right off the glass with my magnet scraper/scrubber, and doesn't grow in the little circles/plates
anyways. But it DOES get kind of hard to get off the back glass, which I scrub less often. It just
seems to grow in a thin layer on everything, not slimy, not hairy, just a green tint. I've included
pictures below (its actually not as green as it appears in the pics, taken with my camera phone
and color is exaggerated). None-the-less, it's very annoying/ugly to me, and given the relatively
low levels of nitrate and undetectable phosphates, very surprising that it hasn't subsided yet!
Any advice on what it might be, and what might be causing it, would be very very very much

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