# Green Dust Algae: What is it and how to control it?



## cS (Jan 27, 2004)

Green dust algae infests my high light 29G. In this same tank, there are no other noticeable algae present. The algae appears to be light loving; but short of reducing lighting levels and/or through an UV sterilizer, what else can I do to curb its growth on the glass walls?

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Plant growth is excellent: no deficiency and/or toxicity that I am aware of. Pearling occurs ~4 hours after the lights are on. I don't test for any parameters, but the following is my weekly fertilization regiment.

Pressurized CO2 at 1.5 bps, with external reactor powered by Rena Filstar XP3 canister filter.

*CALCIUM/MAGNESIUM*
3-6 dGH from CaCO3 & MgSO4.7H2O (0 dGH from tap water)

*NITROGEN*
32.57 ppm NO3/week via KNO3

*PHOSPHORUS*
1.86 ppm PO4/week via KH2PO4

*MICRONUTRIENTS*
1/64 tsp Plantex CSM+B 2x/week 
1/64 tsp Sequestrene 330 (10% FeDTPA) 1x/week

Moderate fish load with feedings every other day of live grindal worms, flakes, or frozen bloodworms...depending on my mood for the day. :mrgreen:

That comes out to be ~4.65 ppm NO3 per day. That's the minimum amount required (in this tank) to keep the leaves of Micranthemum umbrosum large and robust. Aside from being a phenomenally attractive plant, it is quite useful in the determination of the nitrogen needs in my tank.

Please advise. Thank you.


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## Simpte 27 (Jul 16, 2004)

Still new to plants but not new to algae. I believe you're talking about green spot algae. It loves light and to my knowledge some will always be present in planted tanks. I usually use an old credit card to scrape it off. My CAE eats new spots but they get hard really quick so he isn't much use.

Hope this helps.


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## cS (Jan 27, 2004)

It's not green spot algae. At this point, I would be happy if it were green spot or BBA. Hehehe.


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## gpodio (Feb 4, 2004)

Try to reduce the amount of iron you dose and see if that helps. I found I got a lot of dust algae when I tried to use certain celated irons and also when I raised FE levels too much. For some reason my Kent FE bottle produced more dust algae than anything else, Flourish FE on the other hand didn't. I never took it any further than that.

Hope that helps
Giancarlo Podio


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## Cavan Allen (Jul 22, 2004)

We know how much you're adding, but what are your nutrient levels? 

I've had green dust show up when nitrates got either very high or low. 

I add quite a bit of Flourish Iron and don't get it.


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## cS (Jan 27, 2004)

Thank you for your inputs guys. Giancarlo, I'll perform a 90% water change and exclude the Sequestrene 330 dosage in the upcoming week(s) to see if that'll help.

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Cavan, I do not test for any parameters, but employ clues from the tank for guidance.

CO2: Pearling occurs w/i 4 hours after lights are on. Coupled with the absence of BBA and other algae, I believe that there's sufficient dissolved CO2.

Nitrogen: I use Micranthemum umbrosum to gauge how much KNO3 to add because it is the first plant to exhibit low N symptoms with puny leaves. Eusteralis stellata, another plant in the tank, is the 2nd plant to respond to low N with stunted tips. If anything, low nitrogen may be the cause for my green dust algae bout because 32.57 ppm NO3 is the minimum amount I have to add weekly to keep the aforementioned plants from stunting.

Ca/Mg: I do not believe these to be the problems because I have yet to experience any of the problems typically associated with low Ca/Mg, aside from the stunted tips of E. stellata which I ruled out by upping CaCO3/MgSO4.7H2O while keeping [NO3] the same --> same stunted tips until KNO3 dosings are increased.

Phosphorus: I don't know what to make of this parameter. I've played with up to 4ppm PO4 for a while and aside from algae-free Anubias sp., I didn't observe any reduction/aggravation of GDA either. I've had GDA in this tank for a while now. >_<

Micronutrients: I also don't know what to make of this parameter either. The amount I add is just out of convenience because of my tiny dosing spoons.  That and I'll adjust dosages to get some colors out of the 'red' plants.

So, that boils down to Nitrogen and Micronutrients being the two most likely culprits (aside from my high light of course) for my GDA problem...unless I missed something in the analysis?

Maybe I should just start testing to be sure. :-k


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## tsunami (Jan 24, 2004)

You are dosing 32.57 ppm NO3 per week?

On this, I have had the same experience as Cavan --too high or too low NO3. Whenever I tried to raise NO3 levels too high, I got green dust algae on the glass.

I've had large, robust Micranthemum umbrosum leaves at around 10 ppm. This plant may be sensitive to nitrate, but not *that* sensitive.

Knowing you, this extra amount of nitrate you're adding is fairly recent. I would retrace my steps back to the last thing that was changed before this problem occurred.

Carlos[/b]


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## cS (Jan 27, 2004)

Our conversations (particularly those regarding the R. sp. 'Green' when I disclosed the [NO3]) were in reference to the 20G tank, which does not have GDA. :wink: The tank in question is VERY brighly lit (2x 55W w/ AHSupply reflectors + 2x 10W). I could remove the 2x 10W but that would create dark spots that I cannot easily plant low light plants there w/o interfering with the aquascape I am aiming for. Planting stems there resulted in the bending effect, where they gravitate toward the higher lighted areas --> aesthetically unpleasing. I've tried decreasing [NO3] before and time and time again, the M. umbrosum would put out those puny puny leaves. If at first you don't succeed, try try again I suppose. Hehehe. I'll give it another go though. Thanks.

You dose 10 ppm NO3 total per week?


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## plantbrain (Jan 23, 2004)

Akinsendemus and they have flagellated zoospores.
So you scrub them off, then 1-2 hours later it reattaches to the tank walls.

Doesn't attach to the gravel or the plants unless severe.

You can turn off the flow, scrub and quickly vacuum any that settle or run a micro or a UV, do a large water change etc.

Once the tank balances out, this stuff goes away on it's own, I've tried to induce it with several things, no really luck. It'll hang on for a few weeks under very high light but I've seen it grow at 2 w/gal also in some tanks.

If you scrub, vac, turn the lights off for 2-3 days etc, that should kill most of it. Clean the scrub pad also after.

I dose 10-12ppm of NO3 every other day in my high light no fish plant tank, I don't have any algae. PO4 is high also, traces are every other day as well. 5.5 w/gal, 110 w on a 20gal H.

No fish, herbivores etc. No algae also.
Very stable tank as long as I add enough nutrients.

Regards, 
Tom Barr


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## tsunami (Jan 24, 2004)

cS,

No, I dose on the order of ~20 ppm per week (spread out throughout the week, of course). I tend to adjust the amount according to the plant mass in the tank or amount of pruning that was done in the last water change.

That's the amount I need to keep my nitrate levels around 10 ppm.

Carlos


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