# What's the science behind this back glass algae?



## Sarpijk (2 Feb 2021)

Hi all, not my picture but it shows what I mean. Occasionally I will get this type of algae on the back glass which after a while slowly vanishes. Is it because the snails and fish eat it? Is this an indication of sth going well in the tank or the opposite?

Finally how does it always grow in so evenly a few Inches below the water surface?


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## Nick potts (2 Feb 2021)

It's mostly dust algae, spot algae etc.

You'll find that 99% of the time it is on the back glass like the picture because people tend to not clean the back glass, or at least not very often, it can be hard to reach etc, and eventually, in a mature setup it will start to disappear  (it won't go away completely and if you don't clean your glass, eventually the whole tank will start going green), also shrimp keepers like to have this as it's good food source.

As for the being a few inches below the surface in the pic, I suspect that is because that's where the light starts hitting the glass and is less bright above it.


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## Natquascape (2 Feb 2021)

Agree with @Nick potts - do you clean the front glass more often than the back glass. Also, you may get more algae on the back if the water flow in that area is less. Having algae in my opinion is signs of a good mature tank. If you have otto cats, algae eating snails and shrimp, some algae is good. Ottos and shrimp need a mature and stable tank with some algae (no too much algae as the algae will compete for nutrients vs plants). Hope that helps


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## Sarpijk (2 Feb 2021)

I keep various species of hillstream loaches. I do like this type of algae and I would love to have it all year round.


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## zozo (2 Feb 2021)

Aufwuchs... 








						Periphyton - Wikipedia
					






					en.wikipedia.org
				









						Periphyton - an overview | ScienceDirect Topics
					






					www.sciencedirect.com


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## roadmaster (2 Feb 2021)

One small Bristlenose pleco could clean the glass in photo, in under a week.lol 
As they grow larger though,they do tend to rasp on broad leaf plants if sufficient vegetable matter isn't available.
I used to raise long finned albino bristlenose and trade the fry at local fish shop for store credit.


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## Zeus. (2 Feb 2021)

Haven't cleaned the back glass in my 500L since starting the tank 4 years ago


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## Sarpijk (2 Feb 2021)

How do I cultivate this green blanket? Seems to come and go in my low tech. More light? More nutrients?


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## dw1305 (2 Feb 2021)

Hi all,


Sarpijk said:


> How do I cultivate this green blanket?





dw1305 said:


> I think the rocks look much more natural with a patina of biofilm. You won't find any submerged rocks in nature that aren't colonised by plants or animals, unless they are continually scoured by sand etc.
> 
> It isn't quite the same, but what would the <"Statue of Liberty"> look like if they kept on scraping off the copper oxide so she wasn't green?


I'd <"like it as well">.


Sarpijk said:


> More light? More nutrients?


Would be my guess, possibly harder water as well?

cheers Darrel


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## Sarpijk (2 Feb 2021)

Cheers guys thanks for the input.

All my rocks are covered in this algae as seen in the picture. The reason I also want it in the back glass is to offer as much biofilm for the 12 various loaches I keep. My water is already hard. About a week ago I had the whole back full of algae but right now I only have patches! Either something in my tank has caused it to disintegrate or it has been grazed by the loaches, snails and shrimps.


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## ceg4048 (3 Feb 2021)

Natquascape said:


> (no too much algae as the algae will compete for nutrients vs plants)


Hello,
        Algae and plants do not compete for nutrients. This is a myth that was started in the early 1990's and is perpetuated since that time. Algae can survive and feed on nutrients  levels thousands of times less than plants could ever hope to. This is a seemingly minor point but it is actually a very important concept which can scuttle our troubleshooting efforts.

Cheers,


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## RIP22295 (6 Feb 2021)

ceg4048​
Is it true though as Tom Barr I think states that if your plants do well this will make it more difficult for the algae?


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## ceg4048 (7 Feb 2021)

BigGRacing said:


> ceg4048​
> Is it true though as Tom Barr I think states that if your plants do well this will make it more difficult for the algae?



Yes it's absolutely true. Algae are predators and they tend to attack weak and dying plants. Having said that, you still need to do the right things so that the plants do well in the first place.

Cheers,


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## alto (7 Feb 2021)

ceg4048 said:


> Hello,
> Algae and plants do not compete for nutrients. This is a myth that was started in the early 1990's and is perpetuated since that time. Algae can survive and feed on nutrients  levels thousands of times less than plants could ever hope to. This is a seemingly minor point but it is actually a very important concept which can scuttle our troubleshooting efforts.
> 
> Cheers,


So you’re saying that in a nutrient limited system, high levels of algae will have no impact on plant access to those limited nutrients?


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## ceg4048 (7 Feb 2021)

alto said:


> So you’re saying that in a nutrient limited system, high levels of algae will have no impact on plant access to those limited nutrients?


I'm saying that in a nutrient limited system the only flora affected by the limit are the plants. Algae have practically no limit by comparison. They have access to nutrients at a concentration of parts per billion, which is thousands and even hundreds of thousands of times lower than plants. So it does not matter if there are high levels of algae because they have plenty to feed on and can still proliferate at nutrient levels far beyond the lower limit of plants. Plants have large, complex structures which require comparatively vast amounts of nutrition.

So yes, if I read your question correctly high levels of algae has nothing to do with plant access to nutrients because the "limit" is already defined as a concentration below what plants have access to.

Hope this helps.

Cheers,


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