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GSA Algae won't seem to go away

tcyphil

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18 Apr 2022
Messages
9
Location
Canada
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:
IMG_4632.jpg
IMG_4639.jpg
IMG_4638.jpg

IMG_4642.jpg

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:
IMG_4634.jpg

Thanks,
Phil
 

MichaelJ

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9 Feb 2021
Messages
1,690
Location
Minnesota, USA
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
 
Last edited:

Andy Pierce

Member
Joined
27 Nov 2020
Messages
289
Location
Cambridge, UK
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.
 

tcyphil

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Thread starter
Joined
18 Apr 2022
Messages
9
Location
Canada
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.
 

erwin123

Member
Joined
4 Mar 2021
Messages
948
Location
Singapore
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
 
Last edited:

si walker

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Joined
30 Mar 2020
Messages
217
Location
uk
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.
 

tcyphil

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Thread starter
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18 Apr 2022
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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.

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.
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!
 

GHNelson

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Hemel Hempstead
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.

1651474458193.png

hoggie
 

si walker

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Joined
30 Mar 2020
Messages
217
Location
uk
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.
 

tcyphil

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18 Apr 2022
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9
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Canada
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.

View attachment 187773
hoggie
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.


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.
 

MichaelJ

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9 Feb 2021
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Minnesota, USA
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
 

tcyphil

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18 Apr 2022
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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.
 

plantnoobdude

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17 Mar 2021
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uk
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.
 

tcyphil

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18 Apr 2022
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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… 🥲
 

erwin123

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4 Mar 2021
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Singapore
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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