# Green Dust Algae (GDA)



## Hoppy (Dec 24, 2005)

I have been irritated by a green algae that grows on the 4 glass walls of my tank, and which returns within a few hours after I scrape it off. Being stubborn, I just kept scraping every few days. So, I did some searching here and that finally triggered my fast aging brain to do its job! Green dust algae is a unique form of algae, one that can swim around in the tank!

About 10 years ago Tom Barr taught me about this algae, but the lesson gradually faded out for me. When we scrape or wipe it off the glass with water in the tank, we just make it go swimming around until we leave it alone, then it returns to nice, well lighted areas of the tank glass walls, where it very quickly reestablishes its colony. This can happen in just a couple of hours. What you observe is that your newly changed water isn't clear, but seems to remain cloudy. Then a couple of hours later you notice the view into the tank is fuzzy, and if you look at the back surfaces of the glass, you see a thin green coating.

The first thing to do when you have this interesting form of algae is to try to move all of it from the tank to the garbage can. Today I did this by draining the tank to about a 25% level, carefully wiping the band of exposed glass surface, after each 3-4 inches of lowered water, with a fresh paper towel - actually about 3-4 paper towels to wipe all four wall bands. Then, repeating this every newly exposed 3-4 inches of wall. When the water reached the 25% full mark, I carefully wiped the rest of the walls while under water, using about 4-5 paper towels, tossing each one every time it was pretty well covered with green algae. I finished by wiping the whole inside with wet towels to get the last haze of algae.

When I refilled the tank with water it was shocking to see just how clear the water was! I expect to have to repeat this several times before the remaining GDA is just a minor irritant.

I believe Otos eat this algae, and I haven't had any for quite awhile, so I may put 6-8 in the tank to see if they will give me a hand. I just wish my brain had done its job sooner!


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## harrynolan27 (Dec 31, 2015)

I've got the same issue in my tank. Grows nicely all over the front glass and plants. I've just been scrubbing the glass and letting the filter pick it up... Probably why its on my plants haha. Had a similar problem in another tank and I just let it cake the glass until it became very brown and very hard then scraped it and it hasn't come back. Thanks for sharing and keep us updated on how your method works in the long run. This algae is so annoying, I actually started looking at twinstar and algae doctors.


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## AWolf (Jun 13, 2014)

I use a diatom filter while I wipe the walls every couple of weeks. It really helps, along with a UV.


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## LRJ (Jul 31, 2014)

Plantbrain also swears by BNP: http://www.plantedtank.net/forums/23-algae/514985-green-dust-algae-confirmation-cure.html

Definitely did the trick for me. Added one to my tank about a year ago to control GDA. Wiped the stuff out in short order and never a hint since.


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## burr740 (Feb 19, 2014)

That's a good tip on removing it from the glass. 

And yes Otos will definitely chow down on it.


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## Hoppy (Dec 24, 2005)

The problem I have with bristle nosed Plecos is that once you get any of them you have to provide for their needs forever. That means having a significant amount of wood in the tank for them to chew on. I am not at all interested in having wood in my tank - I get BBA enough as it is. Otos don't require anything special, other than algae wafers when there is little algae in the tank.

This morning the tank still looks to be free of GDA! Before, by now the walls would all have a very visible GDA coating.


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## MtAnimals (May 17, 2015)

Hoppy said:


> The problem I have with bristle nosed Plecos is that once you get any of them you have to provide for their needs forever. That means having a significant amount of wood in the tank for them to chew on. I am not at all interested in having wood in my tank - I get BBA enough as it is. Otos don't require anything special, other than algae wafers when there is little algae in the tank.
> 
> This morning the tank still looks to be free of GDA! Before, by now the walls would all have a very visible GDA coating.


x2! I found out the hard way,even with just one BN plec,if you don't provide zucchini for them to munch on,they will chow down on your Hygro Corymbosa leaves.I had 3 large plants that mine destroyed the leaves on.


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## dukydaf (Dec 27, 2004)

Thanks for sharing Hoppy. GDA can be a big bother

I might just be having problems with my memory... I remember the method recommended a waiting time of 2-3 weeks until the glass becomes well covered with algae and it completes its planktonic cycle. After that it is pretty much as described. Worked in all my aquariums.

I was doing this waiting game just after the aquarium finished cycling. Added some otos , next morning window clean.... starved little fish they were.


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## discuspaul (Jul 27, 2010)

AWolf said:


> I use a diatom filter while I wipe the walls every couple of weeks. It really helps, along with a UV.




Agree.
I've used a UV sterilizer with great success. It destroyed all of the GDA in a 75 gal tank in a matter of just a few days.
All you need do is get it free-floating often so the UV can pick it up from the water column & zap it.
Scrape if off the glass several times a day if need be (after the residual has re-adhered to the glass). You'll see the amount of GDA quickly being reduced until it's all gone - took approx. 3 days in my case, and it never returned.


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## Hoppy (Dec 24, 2005)

I'm going to add 12 otos to my 65 gallon tank today. The GDA is still very, very slight, but I can see where it is slowly returning to the prime locations on the glass. I doubt that less than 12 of them would have much chance of keeping it in control. The ones my LFS has are very young, perhaps 3/4 inch long.

EDIT
Yesterday that store had about 2 dozen otos. Today, only 7, so that's all I could get. Maybe that's enough?


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## IUnknown (Feb 5, 2003)

I'd also add that having the tank turn-over 7-10 times really helps to eliminate GDA.


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## Hoppy (Dec 24, 2005)

In 24 hours the 7 otos have not had any observable effect on the slight GDA haze on the glass, which is actually increasing a bit. I'm sure it will take at least a dozen, and probably much more to take care of all of the GDA.


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## Gavin Citrus (Aug 2, 2014)

I have Otos and tons of GDA, I never see them enjoying themselves some GDA. Maybe mine are just lazy, I keep them pretty well fed. I have 7 in 60 gallons.

I need to try the UV, as I hate the GDA.


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## Hoppy (Dec 24, 2005)

If you are willing to deal with plecos you can buy bristlenosed plecos and be sure the GDA will be eaten.


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## MtAnimals (May 17, 2015)

<deleted>


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## Kamilstrom (Oct 18, 2012)

Otos are good just for cleaning plants from GDA, not too much for glass(don't have so powerful mouth like plecos). You can wipe glass in any way necessary the GDA always remain somewhere on plants decoration...and then will slowly return back...😭


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## Hoppy (Dec 24, 2005)

The Otos are not going to help much with GDA. And, as usual, it is hard to get all of the Otos to survive. I started with 7, and have found 3 dead, so far. My experience with them is that those who make it for a month or two will live for years, but that first month does reduce the number considerably.

I can easily see the "tracks" where the Otos eat GDA from the glass, but, as should be expected for such tiny fish, they eat a very small part of the GDA. I may look for the Bristle nosed plecos next. That means adding some wood to the tank, and a few "caves" for them to hide in. The more I read about them the less excited I get about adding them.

Years ago I did get rid of GDA with the "let it grow out" method, but my tank is now so close to us that a disgusting appearing tank is the last thing I want. So, I guess I may be forced to move to a 3 bedroom house, with large rooms:laugh2:


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## Hoppy (Dec 24, 2005)

Yesterday I did my slow drain and paper towel wipe again, removing almost all of the GDA without it dropping into the water. Once again, a day afterwards, the water is still very clear, and no green haze on the glass. If all goes as planned, in a couple of weeks I will do this again, hopefully with even less on the glass when I do it. If you do a routine big water change every week or two you can do this each time, as the water level drops, and it is only a small increase in the work you would usually do when changing water. If this continues to work as it now is, I will just live with the traces of GDA and forget about 100% killing it.


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## Hoppy (Dec 24, 2005)

After another 2 weeks I repeated this process. The amount of GDA is a bit less than the last time, but it is still there. I'm convinced that this is a very effective way to live with GDA, not as effective as using bristlenose plecos, but, if you are like me in not wanting to deal with bristlenose plecos, this is the next best way to live with it. I'm no longer fighting the algae, just keeping it under control, to the extent that it is no longer a problem for me.


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## IUnknown (Feb 5, 2003)

Excel at double dose works as an algecide that gets rid of GDA. Problem I had, it was melting sensitive plants.


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