# GSA and plant deterioration - increase macro dose or supplement PO4?



## Tom101 (2 Feb 2022)

Hi all

I've recently experienced a GSA outbreak and some plant health decline (pinholes, yellowing leaves) in my low tech set up (low light, no Co2). 

During this period tank conditions haven't changed (flow, co2, water change schedule, feeding, lighting)

The only thing I can think of is that my root tabs may have "run out", so I've replaced these, however, the decline seems to have persisted

In this sort of situation, would you recommend dosing Phosphate separately to combat the GSA or just up overall ferts?

Any info appreciated.


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## MichaelJ (2 Feb 2022)

Hi @Tom101   A couple of questions:  How old is the tank?  Can you post a Full Tank Shot (FTS).  What are you dosing at the moment and how often (and how big is your tank) ?
I definitely have had very good experience eradicating GSA with increased PO4 dosing (~10ppm wk) - in combination with other measures, such as lower light intensity.

Cheers,
Michael


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## Tom101 (2 Feb 2022)

Hi @MichaelJ  answers below:

*
Tank age*
Tank is just over 1 year old, cycled from pre-existing filter media. 
Prior to this GSA outbreak, it's had about 3 months of really nice plant growth and colour. 
Unfortunately before that growth spurt it had a pretty bad BBA problem which was solved with improved flow.

*Dosing*
2ml Easy life carbo (daily)
1.5ml TNC complete (daily)
10ml Easy life Algaexit (weekly)
A few calcium cubes for the snails (weekly

*Other info*
Size is 70L
Lighting is Fluvial plant 3.0 - full spectrum @ 16% intensity for 8hrs a day


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## Hufsa (2 Feb 2022)

I checked out your ferts, TNC Complete is pretty low on nitrate and phosphate. 
I would get some more of that into the tank. Not sure if I would increase the dose of the Complete, the ratios are not EI so you'd end up with a lot of extra K and traces.. 
The plants will undoubtedly have gotten some of it from the soil previously, but the soil will start running low at some point, if it hasnt done it already


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## John q (2 Feb 2022)

I think @Hufsa  is correct in saying the phosphate levels are a bit low in comparison to nitrogen but I think you'd be ok increasing the dose of tnc complete a bit. Assuming you're adding 10.5ml a week it will give you this.




Which would equate to approx 10pppm of N03 & 0.9ppm of P04.  
If you were to increase this by 50% to 2.25mls a day I think you'd be fine with the extra k that it would add, also the fe would still only be 0.18ppm p/w. 

Best plan of action would be to try it and see if it helps.


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## MichaelJ (2 Feb 2022)

Hi @Tom101 ,

Your tank look good!  The GSA problem is nothing a bit of tweaking can't fix.

Well, I am going to raise John and @Hufta's good suggestions a bit and say make it a flat 3 ml daily of the TNC Complete.  That will give you about 20 ppm of NO3  1.8 ppm of PO4 and 15 ppm of K all weekly - while your tank is not entirely dense, you do actually have quite a bit of plants there...   Alternatively, or in addition, as I think  the PO4 level might still be too low, based on my experience fighting GSA, is to dose some KH2PO4 in addition, say 0.5 g once per week at least for a month or so  after the WC - which in addition to the TNC @ 3 ml /daily would give you 6 ppm of PO4 in total.

You may also want to dial down the light intensity a smidge and/or add some floating plants such as frogbit - they are excellent at providing shade and as a means to gauge your nutrient levels.

Cheers,
Michael


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## Tom101 (3 Feb 2022)

Hi guys, thanks very much for your suggestions. I'll start upping the TNC as you've suggested. I'm hoping this will generate some improvement.

One thing I did notice, is that my new root tabs (add a week ago) don't contain any Nitrogen or Phosphate (I used the Seachem tabs). Is this a problem I should look to address?

@MichaelJ @Hufsa @John q


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## John q (3 Feb 2022)

Tom101 said:


> Is this a problem I should look to address?


Hi Tom, if you are dosing adequate nutrients in the water column then I don't think you need to be that worried about root tabs, the ones you've added will be fine. 
Plants are perfectly capable of absorbing the things they need through their leaves, some people will suggest they do better when fed this way, others will suggest feeding through the roots is preferable. I don't honestly know which of the above methods works best but I do know plants can grow perfectly well without root tabs. 

Hope that's of some help.


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## Tom101 (4 Feb 2022)

Thanks @John q !


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## Tom101 (8 Mar 2022)

Hi guys

Update on the thread  - it's been a month of dosing upping the daily TNC dose from 1.5ml to 3ml.

GSA is about the same, however, plants are looking a bit worse. Quite a few have now got a brown tinge or edge. Can't quite tell if it's diatoms or another deficiency.

Any thoughts?

@John q @MichaelJ @Hufsa


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## dw1305 (8 Mar 2022)

Hi all, 


Tom101 said:


> it's been a month of dosing upping the daily TNC dose from 1.5ml to 3ml. GSA is about the same however, plants are looking a bit worse. Quite a few have now got a brown tinge or edge. Can't quite tell if it's diatoms or another deficiency.


Could we have a full tank shot, and maybe a couple of close-ups of the worst effected plants?

cheers Darrel


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## John q (8 Mar 2022)

Hiya mate. Its hard to tell from the pictures but are these issues predominantly in the central section of the tank or is it also affecting the plants far right and left, if its the former then we need to question the light intensity. 

+1 for darrels suggestion of fts.


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## Tom101 (8 Mar 2022)

Hi both - shots attached. All plants affected (left, right, centre, multiple species). @dw1305 @John q


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## MichaelJ (8 Mar 2022)

John q said:


> Hiya mate. Its hard to tell from the pictures but are these issues predominantly in the central section of the tank or is it also affecting the plants far right and left, if its the former then we need to question the light intensity.
> 
> +1 for darrels suggestion of fts.



Agreed.  A FTS and and possibly redo the 3rd shot in your original post so we can see the decline.    I think (I might be wrong) that area is also the area that gets the highest light intensity. You want to dial that down for the time being.  Other than that you have to look into flow as well - make sure you don't have any stale areas where nutrient distribution is low or absent.

If you want to experiment by upping the PO4 levels for a while (which have worked for me, and others, against GSA) you will have to dose that separately with Monopotassium phosphate (KH2PO4) or similar a compound.  If your doing 50% WC weekly (35 L) you only need to add 0.25 g per week to reach 5 ppm - with the additional TNC complete you should be covered.

Cheers,
Michael


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## John q (8 Mar 2022)

@Tom101  I'm struggling a bit to get my head around your light settings. My gut instinct is to suggest lowering the intensity a bit, you seem to be getting some growth like side shoots forming and good colouration in the red stems, which suggests there is enough light. However, if I'm right in thinking you have the 22w fluval fixture and this is set at 16%(?) This would equate to your tank only getting 3.52w. The picture looks like it's getting more than this. 

Either way like MichaelJ says double check you've adequate flow in the tank and add a separate source of Po4, Seachem phosphorus will suffice if you don't want to go down the dry salt route. (Increasing this also worked for me in the past against gsa.)

The brown edging is indeed diatoms and should rub off the leaves, just be sure to do a water change after you've cleaned it off the leaves.


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## MichaelJ (8 Mar 2022)

What John says....   It can be hard to judge from a picture, but the light looks quite intense to me as well - nothing like the 16% setting on a Fluvial plant 3.0 (which I believe is 32w)  which is quite low. 

Cheers,
Michael


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## Tom101 (8 Mar 2022)

Thanks for the replies. I'll grab some extra PO4 and crack on with that.

I've double checked my light spec/settings and it is indeed the 32W version at 16% (8hrs). I think the angle of the picture is making it look a bit brighter than it is.

In the past I have experimented dropping below 16% but found that plant health deteriorated (all other factors unchanged).


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## John q (8 Mar 2022)

Tom101 said:


> I've double checked my light spec/settings and it is indeed the 32W version at 16%


Hi Tom,
My bad, assumed it was the smaller version. Sorry for all the questions but I'm just trying to guesstimate the amount of par you have at the bottom of this tank.
If you'd be so kind as to humor me and let me know the distance from the light to the top of the substrate I'd be ever so grateful.

Ta.


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## Tom101 (9 Mar 2022)

Hi @John q no problem at all - I appreciate the help!

Distance from the bottom of the light housing to the top of the substrate is approx 31.5cm.


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## dw1305 (9 Mar 2022)

Hi all,


Tom101 said:


> I've double checked my light spec/settings and it is indeed the 32W version at 16% (8hrs). I think the angle of the picture is making it look a bit brighter than it is.
> 
> In the past I have experimented dropping below 16% but found that plant health deteriorated (all other factors unchanged).


Turn up the <"intensity a bit"> and that will at least take low light away from our possible causes of poor plant growth.

If the plants really do look pale? You could try a bit more magnesium (Mg), you can buy it easily as "Epsom Salts" (MgSO4.7H20) for baths etc  and that is 10% Mg.

If the new leaves are palest? It may be an <"iron (Fe) availability issue">. For iron deficiency you are looking for this effect (below). I like a floating plant because they are adapted to strong light and aren't CO2 limited. I particularly recommend Amazon Frogbit (_Limnobium laevigatum_)  because it has a <"nice green leaf"> and will still grow in very nutrient poor, acid water.




All the other nutrients that cause pale leaves (nitrogen (N), potassium (K) & magnesium) are mobile within the plant and <"it is the older leaves that are chlorotic">.


> This is what Amazon Frogbit looks like, if you <"feed it plenty">.


cheers Darrel


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## Tom101 (9 Mar 2022)

Thanks Darrel - I've actually got some Potassium, Magnesium and Iron lying around so can certainly try those.


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## dw1305 (9 Mar 2022)

Hi all,


Tom101 said:


> I've actually got some Potassium, Magnesium and Iron lying around so can certainly try those.


It isn't going to do any harm. 

With the potassium (K) and magnesium (Mg) you get a pretty quick greening response, if either of those was Liebig's limiting nutrient. The same  applies for nitrogen (N) and phosphorus (P).  The are all mobile within the plant and it can shuffle them to the newest photosynthetic tissue.

It is a bit different for iron (Fe), it very quickly goes out of solution and we need a chelator to ensure Fe++(+) ion availability, and also it isn't mobile within the plant, so it is only new leaves, that grow after iron becomes available again, that are greener. 

cheers Darrel


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## Tom101 (9 Mar 2022)

Good to know - any specific dosages recommended?  (70ltr tank, no co2)


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## John q (9 Mar 2022)

Tom101 said:


> Distance from the bottom of the light housing to the top of the substrate is approx 31.5cm.



Cheers Tom, shallow tank, that makes a bit more sense now. 

Going to add a big caveat here: Trying to guesstimate par readings isn't very accurate, even if you have known calibrated par meter readings from one light fitting the chances are the next one will be slightly different. 
The figures I'm going to guesstimate are based on manufacturer provided figures, which aren't always accurate and hobbyist provided numbers. 

Based on a few fluval light fixtures I think we can hazard a guess and come up with a ballpark figure regards how much par you have at the substrate of your tank; incidently, if you still have the original box for the light it will give you various par readings on there. 

Based on what par numbers I know for the 59w plant 3, 33w aquasky 2 and 16w aquasky 2 ~  I reckon at 100% power your light will produce between 58 ~ 66 par at a depth of 12", that's within a 3" band directly underneath it. This assumes no shading. 
Assuming this number is remotely accurate (?) It then leaves us with the question "what will your light at 16% provide." Well.. if par drop off is linear to percentage reduction (I've no idea if it is) it would give us 62 ÷ 100 x 16 = 9.92 par.


dw1305 said:


> Turn up the <"intensity a bit"> and that will at least take low light away from our possible causes of poor plant growth.



If my long winded guesstimate above is anything like accurate (it might not be) then this could well be correct. It's very unusual I'd suggest doing this but if there is only 10 par at the substrate then this will be getting pretty close to the plants light compensation point, in layman's terms the amount of light they need to actively grow. 
If you did follow this route I'd only increase the light a bit, say upto 20% and see if there's any improvement. 


Fertiliser wise I personally think you're adding enough other than phosphate. If you look at what numbers you're adding some of these nutrients are at 50~75% ei levels. This in my opinion is more than enough in a low light, low tech tank. 




Your phosphate levels are currently at 1.8 ppm po4, I'd raise this to 3 ~4 ppm and see if the new growth with increased light is free of gsa. We don't know why increased phosphate reduces gsa but a number of us have managed to keep it at bay by raising the levels. 

I guess its all about trail and error Tom, I don't claim to have all the answers, just lots of best guesses. 😀


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## Tom101 (9 Mar 2022)

Thanks @John q some great info there. I'll get some Phosphate purchased and crack on with the above. Really appreciate the insights!


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