# GSA Algae won't seem to go away



## tcyphil (1 May 2022)

Hi all,

New to this forum. Like many, I'm having issues with GSA algae for my tank. It's not insanely sever (at least not yet...) but all my plant leaves are turning darkish along with green dots if you look closely. For some reason it only grows on my plants and rocks but not glass. GSA seems to be developing at all locations (doesn't matter how close it is to the light).

From reading forums, it seems like GSA is caused by either lack of CO2 or low phosphate. When i first noticed the GSA, I tested 0 ppm phosphate so I dosed it to 2 ppm but found that it drops to 0 ppm after 1 day. So I started dosing higher and for the last three weeks I've been dosing daily to make sure the tank has 5 ppm of phosphate. For some reason, my tank consumes 2-3ppm daily which is pretty insane considering the low lighting (see lighting info below)? Any ideas what might be the cause of GSA or how I should proceed?

*See photos for reference:*











*Tank Parameters:*

Tank started in November 2021, GSA appeared around early March 2022
11 gallon
Coralife T5NO light x 2 bulbs (pretty low light). Mounted ~4" from water surface.
Photoperiod is 7 hours
CO2 with indicator showing lime green (also did PH test showing 1 PH drop before and after CO2 is turned on)
Cannister Filter providing 106GPH flowrate
Fluval Stratum Substrate
Dosing 1 pump of Tropical Specialized Nutrients and dosing Seachem Fluval Phosphorous to 5 ppm (dosing daily to meet total of 5 ppm in tank).
8 CRS shrimps (rarely feed them pellets)
Biweekly 30-40% water change (every 3-4 days). Treated with Seachem Prime.
Plants: S. Repens, AR mini, Monte Carlo, Eleocharis acicularis

*Water Parameters:*

Ammonia/nitrite: 0
Nitrate: 20-40 ppm (hard to tell with API drop tester). Not sure why my nitrate is so high??? 1 pump of TSN only gives ~3ppm for my tank size. Maybe the tester is bad?
PH: 6.8 before CO2
KH:2
GH:5
Phosphate: 5 ppm
Tap water shows 0 nitrate/nitrite/ammonia/phosphate

*Tank for reference:*



Thanks,
Phil


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## MichaelJ (1 May 2022)

Hello @tcyphil  Looks like your doing a lot of things right there as far as I can tell...  Well, its a small tank (40 L), So I am wondering if you algae "problem" (which aren't that big really when judging from the pictures...)  might be due to fluctuating water parameters? - when you do WC's make sure you match the water parameters in the tank  - perhaps let the tank stabilize a bit and dial the WCs down to say 40% WC  once a week... also look into your flow situation, poor/unstable CO2 delivery is often the culprit (I am not a CO2 user, so I am just _parroting_ what the experts says...   ).  As for the NO3 test, yes that is notoriously hard to test for - its almost impossible to tell if its 20 or 40... based on your dosing it should probably sit around 5 ppm - give or take...

I am sure others will chime in on this...

Welcome to UKAPS! 

Cheers,
Michael


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## Andy Pierce (1 May 2022)

The tank actually looks pretty good to me. Water flow issue is possible and consistent with a lack of relation you have between algae and light levels which is the usual GSA driver.  If what you're seeing is mostly on older lower leaves of stem plants, that's pretty normal and sorted by a semi-regular trim-and-replant-the-tops routine. Still early days for the tank at 4 months so no need to panic.


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## tcyphil (2 May 2022)

Thanks guys. I'll keep an eye on the tank and reduce my water change to once a week. I'll also reposition the flow nozzle so it flows from right to left instead of back to front...maybe that'll help. The GSA develops on most leaves, just to different degrees of algae.


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## erwin123 (2 May 2022)

tcyphil said:


> Hi all,
> 
> From reading forums, it seems like GSA is caused by either lack of CO2 or low phosphate. When i first noticed the GSA, I tested 0 ppm phosphate so I dosed it to 2 ppm but found that it drops to 0 ppm after 1 day. So I started dosing higher and for the last three weeks I've been dosing daily to make sure the tank has 5 ppm of phosphate. For some reason, my tank consumes 2-3ppm daily which is pretty insane considering the low lighting (see lighting info below)? Any ideas what might be the cause of GSA or how I should proceed?


Just to confirm I'm reading this correctly - you are dosing *2ppm PO4 *daily and therefore *14ppm PO4 weekly* for the last 3 weeks? That is a massive amount so the fact that your tank still looks (ok) suggests that excess ferts don't cause algae


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## si walker (2 May 2022)

erwin123 said:


> Just to confirm I'm reading this correctly - you are dosing *2ppm PO4 *daily and therefore *14ppm PO4 weekly* for the last 3 weeks? That is a massive amount so the fact that your tank still looks ago suggests that excess ferts don't cause algae


Well this is interesting. 
I too have GSA 
Added extra PO4 on top of my TNC ferts, all dosed daily. 
After about two months which was yesterday, I decided to test my PO4 as nothing at all was happening (don't normally test).
I expected to see very little PO4 reading in my tank and tap water, convinced that was causing the GSA?
Both readings were through the roof and off the chart for PO4. The API test goes to 10PPM top reading (blue) and my test was ink blue near black!
Also I have cut my light duration and intensity right back. Actually considering snails. Although GSA is basically only on my Anubias plants and rocks.
Any ideas let us know!
Simon.


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## tcyphil (2 May 2022)

erwin123 said:


> Just to confirm I'm reading this correctly - you are dosing *2ppm PO4 *daily and therefore *14ppm PO4 weekly* for the last 3 weeks? That is a massive amount so the fact that your tank still looks ago suggests that excess ferts don't cause algae


Yea that's right. It's pretty nuts...I'm switching to dry ferts soon because the Seachem Phosphorus I bought is running low already. I read somewhere that Fluval Stratum can absorb phosphate though so perhaps its not my plants taking in all that phosphate.



si walker said:


> Well this is interesting.
> I too have GSA
> Added extra PO4 on top of my TNC ferts, all dosed daily.
> After about two months which was yesterday, I decided to test my PO4 as nothing at all was happening (don't normally test).
> ...


That's pretty crazy. Are you running a low tech tank? Maybe it's the lack of CO2 (heard that's usually the other cause for GSA)? Best of luck!


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## GHNelson (2 May 2022)

You need to find a balance when dosing Phosphate!
Each aquarium will be different.
3 to 1 Ratio No3/Po4 is a good starting guide...
Have a look at Gregg's Parameters.....for Phosphate dosing.




hoggie


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## Mr.Shenanagins (2 May 2022)

I’ve found that GSA really enjoys light. Have you recently changed your lighting or even replaced the bulbs?


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## si walker (2 May 2022)

tcyphil said:


> That's pretty crazy. Are you running a low tech tank? Maybe it's the lack of CO2 (heard that's usually the other cause for GSA)? Best of luck!


Yeah it is Low Tech. I also have about 10ppm Nitrate out of the tap. I will get some TNC Lite I think.


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## tcyphil (2 May 2022)

GHNelson said:


> You need to find a balance when dosing Phosphate!
> Each aquarium will be different.
> 3 to 1 Ratio No3/Po4 is a good starting guide...
> Have a look at Gregg's Parameters.....for Phosphate dosing.
> ...


Thanks, I'll double check my Nitrate level once my new tester arrives in a couple weeks. Is 3:1 too much phosphate? I've been reading alot of 10:1 ratios online and perhaps increasing to 5:1 if there's GSA.




Mr.Shenanagins said:


> I’ve found that GSA really enjoys light. Have you recently changed your lighting or even replaced the bulbs?


Nope, same lightbulbs since day 1. There's also no direct sunlight to the tank. I thought of doing a blackout but seems like it doesn't really do much for GSA since existing GSA generally doesn't go away.


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## MichaelJ (3 May 2022)

If you been doing 14 ppm of PO4 weekly for 3 weeks without seeing any progress, that might suggest that P/PO4 is not the place to look and might actually just delay stabilizing the tank which is more important than any dosing_ tweaks _you can make. First and foremost look into your CO2 situation - if you made some changes you should just wait it out a see how the situation evolves. In the meantime you can lower your light intensity a bit. Again, your GSA issue is really not too severe...

Cheers,
Michael


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## tcyphil (3 May 2022)

I've changed my water nozzle to a spraybar flowing right to left so hopefully that provides better water circulation (i also moved the filter intake to the back right corner). As for the water parameters, I'll keep it the same for a few weeks and see if the GSA stops spreading. I haven't done much with my CO2 as plants seem to be growing well and the C02 indicator color seems normal.


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## plantnoobdude (3 May 2022)

MichaelJ said:


> If you been doing 14 ppm of PO4 weekly for 3 weeks without seeing any progress, that might suggest that P/PO4 is not the place to look and might actually just delay stabilizing the tank which is more important than any dosing_ tweaks _you can make. First and foremost look into your CO2 situation - if you made some changes you should just wait it out a see how the situation evolves. In the meantime you can lower your light intensity a bit. Again, your GSA issue is really not too severe...


agreed, if this algae was caused by low po4 then every single tank dosed with tropica will have huge amounts of green spot algae.
what I would do is,
increase flow (gentle but high turn over)
increase co2 
lower light
take out affected plant mass.


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## MichaelJ (3 May 2022)

plantnoobdude said:


> what I would do is,
> increase flow (gentle but high turn over)
> increase co2
> lower light
> take out affected plant mass.


Agreed!!


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## tcyphil (3 May 2022)

Not sure how I can increase the flow without replacing the filter. It’s already a pretty high flow rate for this tank size. I’m hesitant to increase co2 anymore as it might choke out my shrimps. Also the Kh ph test shows good amount of co2 (particularly with my low light). I’ve been taking out the more severely affected leaves but almost every leaf has GSA… 🥲


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## Hanuman (3 May 2022)

tcyphil said:


> From reading forums, it seems like GSA is caused by either lack of CO2 or low phosphate.





			James' Planted Tank - Algae Guide


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## erwin123 (3 May 2022)

tcyphil said:


> Not sure how I can increase the flow without replacing the filter. It’s already a pretty high flow rate for this tank size.





USB pump costs US$5 from China sellers  (I bought several for US$3.50 each during a sale, postage included) I find them super useful for areas of poor flow (which are usually in corners and therefore your pump won't be so visible as it is at the substrate level and hidden by the pumps).

In this video, I'm using it the top as a surface skimmer (why pay so much money for a shrimp killing Eheim 350 when I can use a far more compact usb pump as a skimmer?). I think this is a problem with small tanks like your 11 gallon, traditional surface skimmers are bulky and way too visible.

Since this video, I've placed a filter pad over the intake so its not noisy but still sucks grime from the water surface.


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## tcyphil (3 May 2022)

Nice, I’ll order a few and try them out! Thanks


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## Yugang (3 May 2022)

Hanuman said:


> James' Planted Tank - Algae Guide


Natures workings can be mysterious. How a lack of plant nutrients (CO2 and Phosphate) can let one plant species (GSA) thrive…


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## dw1305 (3 May 2022)

Hi all, 


Andy Pierce said:


> The tank actually looks pretty good to me.


<"Same for me">.

cheers Darrel


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## Andy Pierce (3 May 2022)

tcyphil said:


> Also the Kh ph test shows good amount of co2 (particularly with my low light).


Major alarm bells.  The KH/pH test can't be relied upon when testing aquarium water.  Easiest is to get a drop checker (that's what I use).  Others go with a pH pen for spot measurements looking for a 1 unit pH drop.


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## tcyphil (3 May 2022)

Andy Pierce said:


> Major alarm bells.  The KH/pH test can't be relied upon when testing aquarium water.  Easiest is to get a drop checker (that's what I use).  Others go with a pH pen for spot measurements looking for a 1 unit pH drop.


I have a drop checker as well and it shows lime green by end of day.


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## MichaelJ (3 May 2022)

Andy Pierce said:


> Major alarm bells. The KH/pH test can't be relied upon when testing aquarium water.


I think what you might have meant is that the KH/pH chart can not be relied upon to gauge CO2 levels.

Cheers,
Michael


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## Hanuman (4 May 2022)

I don't see much of an algae issue in that tank. I mean you cannot expect a tank to be 100% free of algae that's just not possible. Your tank looks just fine in my opinion.

As for the PH/KH chart, that chart is theoretically pretty accurate for degassed water as long as there is no other contributors to PH other than carbonates and that's the issue in our tanks because we add soil, woods, ferts etc etc which buffer the water. So you end up with a lower PH before you even start adding CO2.

No CO2 testing method is perfect. DC or PH drop both have their downside. I prefer the PH drop test for multiple reasons specially because you don't have to wait several hours to have and idea where you CO2 is at. Pick the one that suits you most.


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## tcyphil (4 May 2022)

Hanuman said:


> I don't see much of an algae issue in that tank. I mean you cannot expect a tank to be 100% free of algae that's just not possible. Your tank looks just fine in my opinion.
> 
> As for the PH/KH chart, that chart is theoretically pretty accurate for degassed water as long as there is no other contributors to PH other than carbonates and that's the issue in our tanks because we add soil, woods, ferts etc etc which buffer the water. So you end up with a lower PH before you even start adding CO2.
> 
> No CO2 testing method is perfect. DC or PH drop both have their downside. I prefer the PH drop test for multiple reasons specially because you don't have to wait several hours to have and idea where you CO2 is at. Pick the one that suits you most.


Definitely not expecting a 100% algae free tank. I don't mind algae on rocks honestly... it's the GSA on the leaves that's annoying as it makes most of my leaves darker than the rest. I think the algae issue is much worse than what the photos show due to lighting.  Basically roughly 70% of my leaves are like the fourth photo where there's clearly dark GSA growing. Even looking at the Monte Carlo photo, you can see many of the older leaves been darker (those have GSA). Just trying to get a good control of the situation before it gets worse.

*edit for grammar


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