# Green spot algae trouble.



## skinskin72 (Jun 17, 2010)

I'm new to the planted aquarium world. I have a 26 gallon bow front that is heavily planted, with 13 fish, swordtails, mollies, a few tetras, and two mystery snails. I have 96 watts, two 6000K, and two roseate T5 lamps. The roseate lamps run for twelve hours daily, and the 6000k's for ten. The aquarium has been up and running for three months now with good growth results. I was having a problem with stag algae, and green spot algae. I double dosed Flourish Excel for two weeks until all the stag algae was gone, but there was little damage done to the GSA. I discontinued the double dosing due to the effects on my cork screw vals. I scrub the glass clean, and do a 20% water change each week. I'm also starting to develope slightly hazey green water. Am I keeping the light on too long?


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## Jeff5614 (Dec 29, 2005)

You might try going to 10 hours a day and using 3 bulbs instead of 4. You didn't mention any dosing besides Excel. GSA is also linked to low PO4 levels so you might try upping your PO4 a bit or start adding some if you aren't currently.


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## skinskin72 (Jun 17, 2010)

I knocked off two hours on the lights, and the GSA has reduced some what. The only other things I add to the tank are Flourish twice a week, and flourish plant tabs. I'll give the PO4 a shoot and see what happens. What is a good level to shoot for? The stag horn algae has also returned on my drift wood. Started double dosing the Excel again yesterday. I hope the vals can hang in there.


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## EntoCraig (Jun 7, 2010)

I only run my lights for 7.5 hours and dose Metricide every other day. Minimal algae problems. Algae is natural... do you have any algae eating fish or shrimp?


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## DarkCobra (Jun 22, 2004)

That's quite a bit of light. I would also say 8 hours, and reduce intensity if you can.

Excel is not an adequate substitute for real CO2 at your light level. It also has no effect on GSA.

Staghorn and green water may be triggered by ammonia, sometimes even at levels too low to detect with test kits. Some causes of ammonia:

* Tank overstocked with fauna.
* Dirty substrate.
* Dirty or inadequate filtration.
* Nutrient deficiencies (including CO2) slowing plant growth, which leads to slow plant uptake of ammonia.
* Large excess of nitrate, which leads to plants uptaking that instead of ammonia.

Target levels of phosphate are 1-2ppm. Even if you already have enough (or more than enough), adding a bit more often seems to help with GSA, though I can't explain why.

Look into as many of these possibilities as you can, as there may be more than one factor; but the light/CO2 imbalance is the biggest issue.


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## Canuck (Apr 30, 2009)

DarkCobra said:


> * Large excess of nitrate, which leads to plants uptaking that instead of ammonia.


I've never seen this listed as a cause before. Wondering if you can cite a source.

Thanks and sorry for being off topic.


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## EntoCraig (Jun 7, 2010)

Canuck said:


> I've never seen this listed as a cause before. Wondering if you can cite a source.
> 
> Thanks and sorry for being off topic.


Its actually pretty common knowledge but here are a few links:

http://freshaquarium.about.com/od/algae/a/attackalgae.htm

http://www.thetropicaltank.co.uk/algae.htm

http://freshaquarium.about.com/od/watercare/a/nitrates.htm

http://www.aquaticcommunity.com/aquariumforum/archive/index.php/t-5967.html

http://www.tropicalfishkeeping.com/aquarium-plants/what-relationship-between-nitrate-algae-30605/

While high nitrates could be the problem, I find its the Phosphates that are usually the real issue.

Good luck!


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## Canuck (Apr 30, 2009)

Thanks, I was hoping for something a little more substantive, than assertions.


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## captain_bu (Oct 20, 2007)

Info in links seems questionable at best...

Agree the OP has a lot of light and most likely would benefit from reduced light, pressurized CO2 and a comprehensive dosing regime. Bi-weekly water changes and keeping the tank and filter clean is a good idea too.


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## EntoCraig (Jun 7, 2010)

captain_bu said:


> Info in links seems questionable at best...
> 
> Agree the OP has a lot of light and most likely would benefit from reduced light, pressurized CO2 and a comprehensive dosing regime. Bi-weekly water changes and keeping the tank and filter clean is a good idea too.


Seems pretty straight forward to me. The best thing anyone can do is know your setup and know what is excess, whether its lights, co2, nitrates, or anything else.

:icon_cool


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## DarkCobra (Jun 22, 2004)

Plants can get their nitrogen from both nitrates like KNO3, and ammonia.

They do have a preference for ammonia, or so I hear. But plants' uptake ability is not unlimited. Do plants uptake as much ammonia if they're stuffed with nitrates at 50ppm, as they would if nitrates were at a reasonable 20ppm? I don't think so. No source or reference needed, it's common sense. I don't need a research paper to tell me that if I want to finish the 16oz. ribeye at the steakhouse, I'd better not fill up on the free bread beforehand. 

The nitrates aren't the cause of algae, the ammonia is. If everything is set up right, you'll have very little ammonia; and you can go crazy with nitrates and never have a problem. But if you have other problems causing elevated ammonia, then excess nitrates can _appear_ to cause algae; and reducing nitrates can indeed reduce or eliminate the symptom, even if the real problem still exists. I've been there and done that.

Obviously, solving the real problem is preferable, and that's why I listed the excess nitrates possibility last. I just prefer to give a variety of options.

Many of those algae guides claim that various algae are caused by excessive nitrates. Those claims aren't just made up, they're from experience; because people actually reduced algae by reducing nitrate. Other people claim that excess nitrates don't cause algae, and that is from their experience too.

Instead of dismissing either side's experience as false, questionable, or assertions, try to learn from everyone. Both sides' experience can simultaneously be valid and explained, with the right explanation. Even if that explanation isn't scientifically proven, if it works it's better than no explanation at all.


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## EntoCraig (Jun 7, 2010)

Thanks for the info and clarification DarkCobra, learned something new. Makes sense


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## Captivate05 (Feb 23, 2010)

DarkCobra said:


> Plants can get their nitrogen from both nitrates like KNO3, and ammonia.
> 
> They do have a preference for ammonia, or so I hear. But plants' uptake ability is not unlimited. Do plants uptake as much ammonia if they're stuffed with nitrates at 50ppm, as they would if nitrates were at a reasonable 20ppm? I don't think so. No source or reference needed, it's common sense. I don't need a research paper to tell me that if I want to finish the 16oz. ribeye at the steakhouse, I'd better not fill up on the free bread beforehand.
> 
> ...



Very reasonable explanation.


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## Thejosher (Aug 8, 2019)

Thanks for the help guys. I have green spot algae taking over my plants and this thread gave me some good starting points.


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## tolstoy21 (Nov 13, 2018)

skinskin72 said:


> I knocked off two hours on the lights, and the GSA has reduced some what. The only other things I add to the tank are Flourish twice a week, and flourish plant tabs. I'll give the PO4 a shoot and see what happens. What is a good level to shoot for? The stag horn algae has also returned on my drift wood. Started double dosing the Excel again yesterday. I hope the vals can hang in there.


Yeah, check your Phosphate levels. I had similar problems with GSA before checking my phosphates only to discover they were at zero.

According to what I've heard from Seachem, your phosphates should be in the ballpark of 10:1 with your nitrates, meaning if your total nitrate level is at 10 ppm, the your phosphates should be around 1 ppm (try not to exceed 1 ppm). They also claimed (and I actually found this to be true) that if your ratios are somewhat balanced, your plants will take up more nitrates, and initially you'll see a decrease in your nitrate levels. If I remember correctly, the claim was that when there is an imbalance of phosphate to nitrate, your plants are having a harder time utilizing the available nitrate in the water, which then feeds the GSA. On the flip side, excesses of phosphates can also create algae. So balance is the key. 

At least this is what a Seachem rep was preaching, and I have found it to work in my tank. I had a TON of GSA on my anubias and now keep my and nitrates between 10 and 20pm and my phosphates at about 0.5 ppm (the levels probably fluctuate between 0.25 and 1ppm during the dosing schedule, but most of the time I check they seem in the 0.5ppm range). At about 20ppm nitrate I do a 30% water change. 

Since Ive started dosing phosphate, my GSA has stopped completely on new growth, but i did have to bleach dip the plants to kill off the GSA that had already formed on those. I have found that getting the exact ratio of 10:1 to be hard, but if you're in the ballpark and you should be fine.


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## fish+plants (Aug 16, 2019)

If I am totally off here, I apologize. I am not the expert the others are for sure! I found that my oto catfish do an amazing job on green spot algae on glass and algae on plants; just a thought.


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## Triport (Sep 3, 2017)

I have never had any fish that did anything to control GSA but also the only time I have ever had it be a big problem was tanks that I knew were overstocked. It is easy enough to scrape off glass (super annoying in acrylic tanks though) but can be problematic for slow growing plant leaves like Anubias.


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