# Persistent GDA on plants



## RickyV (21 Nov 2022)

Hello UKAPS! I recently made my first post on here on the CO2 thread asking about optimizing the CO2 in my tank. This post was made because I am assuming my GDA was in part due to improper CO2. However after making some changes such as, reducing temp from 28C to 25C, reducing light intensity from 100% to 50% (3 Chihiro's WRGB II pro 90), increasing CO2 injection, and increasing fertilization, I still have not seen much of an improvement on the GDA.

 From what I understand algae growing on plants means they are unhealthy and leaching NH4 which the algae eats. So I need to figure out what is wrong with my plants. I am guessing I either still do not have enough CO2, or I am not fertilizing enough. 

The low CO2 seems unlikely, because my drop checker is lime green at lights on, and it is getting close to yellow at the end of the photoperiod, if I increase the CO2 injection just a little bit my fish will start breathing really heavy, and I have plenty of flow as I have a 20000 LPH pump (though I guess low flow areas are still possible). I am getting a pH probe to get a better idea of the CO2 levels.

As for fertilization I am dosing the fertilizer in the pictures below, it says to dose 5 ml per 20 gallons(75 liters). I am dosing slightly under this at 80ml daily for total system volume of 1325 liters (350 gallons). I do the weekly 50% water changes. It is possible I should be dosing a lot more for my plant mass, I am not sure. 





Here are some pictures of my plants, as you can see they all have a bit of GDA on them. The plants that have the most obvious sign of deficiency is the amazon sword, and the the Brazilian pennywort as the new growth looks really pale but maybe it is normal. The rotala bushes were recently trimmed.


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## MichaelJ (21 Nov 2022)

Hi @RickyV,
I am not a CO2 user, but I think there is still a good chance this is (still) a CO2/flow/nutrient distribution issue.  Only based on a rough _off the top of my head_ calculation, assuming 50% Weekly WC, I think your dosing is _probably ok, _but I also don't think you will go wrong by increasing it a bit and see how that goes as you do have a fair amount of plants there and it is a high tech tank. Again, I am not a CO2 expert, and I am sure some of our CO2 experts will chime in.

Cheers,
Michael


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## RickyV (21 Nov 2022)

My pH pen just arrived and the pH of the tank halfway in the photoperiod is 6.15, the pH of my tapwater is 7.7. I'll check the pH tomorrow throughout the day to know how much my pH drops and changes throughout the day.


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## Yugang (21 Nov 2022)

Your CO2 seems already dangerously high for your lifestock, seems not a likely cause, and would be better at a lower (not above 1.4 drop) and stable level.

What water do you use for 50% WC?  Are you remineralising?


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## Witcher (21 Nov 2022)

Yugang said:


> Your CO2 seems already dangerously high for your lifestock


This.


RickyV said:


> However after making some changes such as, reducing temp from 28C to 25C, reducing light intensity from 100% to 50% (3 Chihiro's WRGB II pro 90), increasing CO2 injection, and increasing fertilization, I still have not seen much of an improvement on the GDA.



Hey @RickyV what's your water parameters in general? Hardness, Ph, NPK and Fe to name them first? I doubt you re-mineralize RO etc for such a large quantities so assuming it's a tap water.

Your plants look generally healthy (no melting etc) but with obvious algae which are a chancers so if it was my tank I'd lower the amount of CO2 and ferts (but really difficult  to estimate how much without knowing water parameters at the first place) and keep the light (and probably temp too) on the high side - both high light and high temp increases metabolism in plants (both lower and higher) which will help with quick depleting of nutrients otherwise available for algae. Higher plants have greater capability of storing nutrients than algae so in the race for food former will win.
Ps. Mg which can be seen as an ingredient of micros on your 2nd image of ferts is not a micronutrient so I'd think twice before using ferts from the company stating sth like that. Probably low amount of Mg can be also contributing to the problems but again - difficult to say without knowing your water parameters.


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## RickyV (22 Nov 2022)

Yugang said:


> Your CO2 seems already dangerously high for your lifestock, seems not a likely cause, and would be better at a lower (not above 1.4 drop) and stable level.


I thought the CO2 was probably pretty high since some of my fish do look a little stressed. But at the same time I hear CO2 being too high for the fish does not mean it is sufficient for the plants. But I would like to keep fish in my tank so I do not want to have dangerous levels of CO2 in my tank.



Witcher said:


> Hey @RickyV what's your water parameters in general? Hardness, Ph, NPK and Fe to name them first? I doubt you re-mineralize RO etc for such a large quantities so assuming it's a tap water.


I do use tap water, below is the water report from a year ago. I will need to test the current parameters in my tank and get back to you. Tomorrow is actually water change day so it will be the perfect day to test. I will need to get a test kit for K, and Fe. Tomorrow I will test the pH before CO2 on and at lights on and at different points in the day to give you guys a better idea of the CO2 levels in the tank.


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## erwin123 (22 Nov 2022)

Normally, I would say that you should remove the algae-infested leaves - on the assumption that the leaves with algae are unhealthy and they are unlikely to 'recover' The plant will be focusing its energy on new growth and letting these unhealthy leaves rot. 
But this is a big tank and there seem to be a lot of affected leaves.... 

Another possibility would be to do a 72-hour blackout which is very effective in my experience in eliminating GDA.  This is in effect a 'reset' of the tank. It does not mean that algae won't come back, but at least it gives your plants a 'head start'....


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## Yugang (22 Nov 2022)

Magnesium seems to be the cause to me, try Epsom Salt for remineralising.


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## RickyV (22 Nov 2022)

erwin123 said:


> Another possibility would be to do a 72-hour blackout which is very effective in my experience in eliminating GDA. This is in effect a 'reset' of the tank. It does not mean that algae won't come back, but at least it gives your plants a 'head start'....


Yeah I do try to remove the really bad leaves at during each water change, but as you said essentially all my plants are affected lol. I have considered a black out. I was just afraid it might not be effective for the algae and also harm the plants in the process. But it sounds like 3 days without light should not affect plants much.


Yugang said:


> Magnesium seems to be the cause to me, try Epsom Salt for remineralising.


This makes sense as the fertilizer I use says 0.33 ppm of Mg per week, and the water report has really low Mg already. And it does seem that older leaves are more affected (just hard to tell what exactly because they are fully covered by GDA). I just read on 2 hr. aquarist an EI level of magnesium per week is 5 - 10 ppm. Is this what I should aim to add?


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## Yugang (22 Nov 2022)

RickyV said:


> This makes sense as the fertilizer I use says 0.33 ppm of magnesium per week, and the water report has really low mg already. And it does seem that older leaves are more affected (just hard to tell what exactly because they are fully covered by GDA). I just read on 2 hr. aquarist an EI level of magnesium per week is 5 - 10 ppm. Is this what I should aim to add?


I would go for 10 ppm, that also balances with the Ca in your water.  I add 20 gram Epsom Salt weekly to my 250 l tank, 50% WC, so you will probably need a bit more than 100 gram weekly. If it is indeed Mg, you should see results pretty fast. Some of your plants do not look happy, looks like some chlorosis as well, this may cause the algae. CO2 is associated with thread algae, not with dust algae.



RickyV said:


> But it sounds like 3 days without light should not affect plants much.


I would try the Mg first, as a blackout does not address the possible root cause (unhealthy plants)

EDIT:
1. Lowering CO2, which I would strongly recommend, is tough for your plants. Do it slowly, and when evaluating the benefit of Mg take into account that plants may feel angry about CO2 for a few weeks. You may see some new algae, BBA and thread, appearing as well.
2. Do NOT try a blackout with high CO2 on. You would reduce the O2 production, and gas the fish and shrimp with CO2.


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## RickyV (22 Nov 2022)

Yugang said:


> I would try the Mg first, as a blackout does not address the possible root cause (unhealthy plants)


Thanks I will start adding some Epsom salt to my tank and see what happens.


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## RickyV (22 Nov 2022)

Yugang said:


> 1. Lowering CO2, which I would strongly recommend, is tough for your plants. Do it slowly, and when evaluating the benefit of Mg take into account that plants may feel angry about CO2 for a few weeks. You may see some new algae, BBA and thread, appearing as well.
> 2. Do NOT try a blackout with high CO2 on. You would reduce the O2 production, and gas the fish and shrimp with CO2.


Makes sense, I will reduce the CO2 very slowly. I see I definitely don't want to gas my fish!


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## plantnoobdude (22 Nov 2022)

reduce co2 first…
increase ferts (maybe) @MichaelJ 
BUT NOT MICROS!!
Those micros are already very high and if you need more, you should probably venture into other mixes, or complimenting the mix with other salts.
A lot of your pics show very clear chlorosis. Fe, Mn and Mg are the cause here. I would try other compounds such as Fe dtpa, Eddha, Gluconate. I’ll tag in some friends here who have some experience with harder water and high tech @KirstyF @Hufsa 

Your dose is currently 0.5 Fe weekly. I dose 0.0875 Fe weekly in my high tech. When I used to dose my APFUK mix, I always had issues with chlorosis, but I even tried up to 1ppm Fe with no improvement. At this point I was desperate, so I would try anything. I decided to start making my own micros at a very Low level compared to before (1ppm Fe to 0.1ppm) believe it or not, all symptoms of chlorosis disappeared. I have pictures of this, and have posted them somewhere on this forum. I use DTPA Fe now, but my tanks have quite soft water, so that is sufficient, for more advice on chelates and hard water.. I would ask kirstyF! 

Perhaps adding Mg will help, but I feel it won’t take the tank all the way to where you want it.

So to conclude. 

Bump up macros (probably not needed) 
Lower co2
Touch up Mg
And fiddle with different chelates in your micro nutrients
(If you need advice I am more than happy to help!)


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## dw1305 (22 Nov 2022)

Hi all,


plantnoobdude said:


> A lot of your pics show very clear chlorosis. Fe, Mn and Mg are the cause here.


  Because your water is relatively calcium (Ca) rich nutrient deficiencies involving magnesium (Mg) and iron (Fe) are more likely.  Looking at the water report I'm going to guess you have enough manganese (Mn) and magnesium (Mg), although adding some more magnesium definitely wouldn't hurt.  You also have a lot of sodium (Na), but there isn't a whole lot you can do about that.

I think there are signs of chlorosis (in the new leaves) as well. It is very likely to be iron (Fe) deficiency, because it is the new leaves that are affected and that means a  non-mobile element . 

Have a look at <"Frogbit taken a turn"> and <"FE EDDHA">.

cheers Darrel


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## jaypeecee (22 Nov 2022)

Witcher said:


> Mg which can be seen as an ingredient of micros on your 2nd image of ferts is not a micronutrient so I'd think twice before using ferts from the company stating sth like that.



Hi @Witcher
For a similar reason, I'd be concerned about the Macros separately listing P and PO4. Also, N and NO3. The Micros bottle also states DGH of 0.02 ppm/degrees. Very odd.
JPC


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## plantnoobdude (22 Nov 2022)

jaypeecee said:


> Hi @Witcher
> For a similar reason, I'd be concerned about the Macros separately listing P and PO4. Also, N and NO3. The Micros bottle also states DGH of 0.02 ppm/degrees. Very odd.
> JPC


Why? 
The N-NO3 conversion is correct at about 4.4
And the P-PO4 conversion is correct at around 3.

I suspect the dgh of 0.2 is how much will be supplied by the fertiliser? (I’m guessing from the small amount of Mg)


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## RickyV (22 Nov 2022)

plantnoobdude said:


> A lot of your pics show very clear chlorosis. Fe, Mn and Mg are the cause here. I would try other compounds such as Fe dtpa, Eddha, Gluconate.


This makes a lot of sense since pale new growth has been pretty prevalent. For some reason I just assumed it was normal and thought the leaves would darken as they age, but they only degraded which made me think it was a macro deficiency. I see now it is very clear this is iron deficiency.


dw1305 said:


> Have a look at <"Frogbit taken a turn"> and <"FE EDDHA">.


Interesting reads, learned a lot! So from what I understand although plants need very tiny amounts of iron, because my water is hard almost none if any iron is available to my plants, hence the Fe deficiency. So It seems a chelator will help with this, it looks like the two recommended ones are DTPA and EDDHA. EDDHA causes a tint in the water which I would not like so DTPA should be fine right? 
According to the dosing calculator I only need 2.41 grams of Fe DTPA 11% for 1325 liters (350 gallons) to raise the Fe by 0.2ppm. Is this a good target?


jaypeecee said:


> For a similar reason, I'd be concerned about the Macros separately listing P and PO4. Also, N and NO3. The Micros bottle also states DGH of 0.02 ppm/degrees. Very odd.
> JPC


Interesting I did not catch this. NilocG is pretty popular here in the US and I have only heard good things which is why I went with them. They do sell some Fe DTPA NA IRON CHELATE SELECT SALTS (FE)


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## dw1305 (22 Nov 2022)

Hi all,


RickyV said:


> ...... So from what I understand although plants need very tiny amounts of iron, but because my water is hard almost none if any iron is available to my plants, hence the Fe deficiency. So It seems a chelator will help with this, it looks like the two recommended ones are DTPA and EDDHA. EDDHA causes a tint in the water which I would not like so DTPA should be fine......


That is it.  

The  other thing I should have said is that it is <"only new leaves">, grown after iron (Fe) deficiency is <"no longer limiting growth">, that will be green. 

That was one reason I originally used _Lemna minor_ ("Duckweed") for the <"Duckweed Index"> (I now prefer <"Amazon Frogbit"> (_Limnobium laevigatum_)), it has a <"very quick turn-over of leaves">.


RickyV said:


> Interesting reads, learned a lot!


You might be interested in <"MG/FE deficiency in S. Repens and Rotala Indica"> & <"Duckweed Index says Nitrogen please?">.

cheers Darrel


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## RickyV (22 Nov 2022)

dw1305 said:


> You might be interested in <"MG/FE deficiency in S. Repens and Rotala Indica"> & <"Duckweed Index says Nitrogen please?">.


Thanks will take a look at them.

Looks like CO2 may not be as high as once thought. Here are the readings so far in the day,
8:00 am pH 7.4 CO2 Turns on
9:00 am pH 6.85
10:00 am pH 6.68
10:30 am pH 6.61 Lights on


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## jaypeecee (22 Nov 2022)

plantnoobdude said:


> Why?
> The N-NO3 conversion is correct at about 4.4
> And the P-PO4 conversion is correct at around 3.
> 
> I suspect the dgh of 0.2 is how much will be supplied by the fertiliser? (I’m guessing from the small amount of Mg)


Hi @plantnoobdude 

I should have made myself clearer.

I'm not questioning the conversion. All that was necessary from the manufacturer was to provide nitrogen and phosphorus figures for NO3 and PO4. This is what the aquarist wants to know. And, is the General Hardness of this fertilizer 0.02ppm or 0.02 degrees? I'm not sure why this figure is quoted on the bottle because both figures are very low and of little relevance. Or, am I overlooking something?

JPC


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## MichaelJ (22 Nov 2022)

jaypeecee said:


> General Hardness of this fertilizer 0.02ppm or 0.02 degrees? I'm not sure why this figure is quoted on the bottle because both figures are very low and of little relevance. Or, am I overlooking something?


Hi @jaypeecee , The bootle says ppm/degrees.   Only degrees apply to the GH. The minerals you add with this Micro/Trace product (predominantly the 0.11 ppm of Mg) will indeed add ~0.02 GH (0.11 / 4.34 ~= 0.02) to the water based on the dosing recommendation, but putting it on the bottle is obviously utterly superfluous as you said.

Cheers,
Michael


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## LMuhlen (22 Nov 2022)

It might be that the supplier is informing that it won't increase the GH significantly, since it may be a concern of their clientele that a fertilizer would increase the GH undesirably. So they are stating, it only increases 0.02 dGH, no need to worry.


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## RickyV (22 Nov 2022)

I felt like I should start a journal on this tank so I will be posting updates on how the plants respond to the iron DTPA and magnesium there. 1200L High Tech Planted Tank


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## jaypeecee (22 Nov 2022)

dw1305 said:


> You also have a lot of sodium (Na), but there isn't a whole lot you can do about that.


Hi @dw1305  & @RickyV 

Is it not possible to 'dilute' RickyV's tap water to lower the sodium level? I just had a quick look at a typical range of sodium figures for my tap water here in the UK. The range is 19 to 38 mg/litre.  RickyV is seeing 33 to 81 ppm. Ricky, are you on well water? I ask because I see that you are in Texas.

Of course, dilution may be easier said than done. Would the use of RODI or rainwater be a viable option? Of course, in saying this, sodium may not be the culprit. There is not a lot of readily-available information about the effects of sodium on aquatic plants. But, I'll dig a bit deeper.

JPC


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## jaypeecee (22 Nov 2022)

MichaelJ said:


> Hi @jaypeecee , The bootle says ppm/degrees. Only degrees apply to the GH. The minerals you add with this Micro/Trace product (predominantly the 0.11 ppm of Mg) will indeed add ~0.02 GH (0.11 / 4.34 ~= 0.02) to the water based on the dosing recommendation, but putting it on the bottle is obviously utterly superfluous as you said.


Hi @MichaelJ 

Thanks for clarifying what I was trying to say. Good on ya!

JPC


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## MichaelJ (22 Nov 2022)

RickyV said:


> I thought the CO2 was probably pretty high since some of my fish do look a little stressed. But at the same time I hear CO2 being too high for the fish does not mean it is sufficient for the plants. But I would like to keep fish in my tank so I do not want to have dangerous levels of CO2 in my tank.
> 
> 
> I do use tap water, below is the water report from a year ago. I will need to test the current parameters in my tank and get back to you. Tomorrow is actually water change day so it will be the perfect day to test. I will need to get a test kit for K, and Fe. Tomorrow I will test the pH before CO2 on and at lights on and at different points in the day to give you guys a better idea of the CO2 levels in the tank.
> View attachment 197968



@RickyV, just wondering if you're running your city water through a household softener or purifier system - very common here in the United States as you know, and many do not really think about or know the implications. If so, what the water report states  will in many respects (mainly Ca/Mg and Sodium if using NaCl pellets) be completely different from what you will actually get out of your indoor taps... just wanted to make sure!  

Cheers,
Michael


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## RickyV (22 Nov 2022)

jaypeecee said:


> Is it not possible to 'dilute' RickyV's tap water to lower the sodium level? I just had a quick look at a typical range of sodium figures for my tap water here in the UK. The range is 19 to 38 mg/litre. RickyV is seeing 33 to 81 ppm. Ricky, are you on well water? I ask because I see that you are in Texas.


I'm not on well water. I do have an RODI unit I use for my reef tank, but It wouldn't be too practical to use for my planted tank right now as I would need a big storage tank for water. And I don't want to go through too many RODI filters lol. 


MichaelJ said:


> just wondering if your running your city what through a household softener (very common in the States, and many do not really think about the implications)... just wanted to make sure!


I don't believe I am.


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## KirstyF (22 Nov 2022)

So, I’ve a hard water tank and this chlorosis thing is a bit of a pet project for me at the moment. 

I note your micro info doesn’t actually advise on whether or not the Fe is chelated at all so that’s probably less than helpful for you (unless it mentions this somewhere else on the packet?) 

EDTA is stable up to 6-6.5ph and DTPA is stable to up to a PH of 7-7.5 (depending on source information) though note that the higher it gets, the less iron is available, and EDDHA goes up to a Ph of 9 or thereabouts.

Your tank it seems will exceed a Ph of 7 when Co2 is off, so, even with DTPA, by the morning after your micro dose, it could be that most of that Fe is no longer available. 

EDDHA may solve that issue but the stronger the chelate, the tougher it is for the plant to access it. (And it’s pink😫) 

So what’s the best solution?  I think perhaps more than one road to Rome, but…..

I instigated some lovely chlorosis in my tank at 0.1ppm of Fe DTPA. It did not take long before my plants started to get pretty grumpy.

I tried an increase to 0.3ppm DTPA, and a combination of DTPA and EDDHA, also at 0.3ppm, without seeing improvement but a combination of DTPA and Fe gluconate (entirely unchelated) at 0.3ppm has done wonders.

This is counterintuitive, as Fe gluconate, being unchelated, is the least stable option and likely to remain available for only a short period. It is however super easy for the plants to uptake and likely to be preferably utilised. 

So, plants get to suck up that Fe gluconate nice n quick and hey presto….happy plants! 

Probably wouldn’t work if you were only dosing once pw of course, but on a 3xpw regime, it’s still doing ok for me. 

I’d also have to say that I’m still testing, and my next plan is to remove the gluconate again to see if/how long it takes for chlorosis to show up (ie, is the experience repeatable) and perhaps to see whether an increase to DTPA only at 0.5ppm gives similar/better/worse results. I’d also be interested to test gluconate only and establish the minimum level the plants would be happy with.

I believe it’s possible that I may find that lower doses of the unchelated Fe gluconate could give better results than higher doses of the chelated products, despite it being a hard water tank…..but there’s a bit more work to do.

For yourself, it depends on what you want to achieve. I’m mixing my own Micro’s and Macro’s so have full control.  

If, however, you want to carry on using your current micro mix as a base, it would be helpful first to understand whether the Fe in it is chelated to any level, and you could just try boosting this with some gluconate!! 

Downside, it’s likely that pound for pound gluconate is gonna cost you more!! 

You could also try adding some DTPA on top of your current base mix but I can’t tell you how much you’ll need before you see results. That would depend on just how little your plants are getting from the 0.5ppm of whatever Fe is already in the tank.


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## MichaelJ (22 Nov 2022)

RickyV said:


> I don't believe I am.


Do you know the GH level by measuring the water (e.g API GH test kit) coming out of the tap you're using for the tank?

Cheers,
Michael


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## RickyV (22 Nov 2022)

KirstyF said:


> If, however, you want to carry on using your current micro mix as a base, it would be helpful first to understand whether the Fe in it is chelated to any level, and you could just try boosting this with some gluconate!!





KirstyF said:


> You could also try adding some DTPA on top of your current base mix but I can’t tell you how much you’ll need before you see results. That would depend on just how little your plants are getting from the 0.5ppm of whatever Fe is already in the tank.



I just emailed customer support to find out what Fe is in the micro packets. I will probably add some iron DTPA in my micro bottle and see what happens. The Fe gluconate helping is interesting I may also try this if the DTPA does not help.  I guess it depends on what Fe is in my fertilizer.


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## RickyV (22 Nov 2022)

MichaelJ said:


> Do you know the GH level by measuring the water (e.g API GH test kit) coming out of the tap you're using for the tank?


I need to get a GH test kit, I thought I had one but only had kH.


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## MichaelJ (22 Nov 2022)

RickyV said:


> I need to get a GH test kit, I thought I had one but only had kH.


Yes, get this kit.  Considering the water report, if your household tap water GH comes out at 0-2 GH its almost certain your city water runs through a softener system. 

Cheers,
Michael


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## RickyV (22 Nov 2022)

So here is an update on CO2. It looks like it takes quite a while for my tank to get the 1 pH drop. Here is the graph so far. I guess this means I need to increase surface agitation, and increase injection? I guess its probably best to not mess with the CO2 right now and see how plants respond from the chelated iron and Mg?


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## John q (22 Nov 2022)

RickyV said:


> I guess this means I need to increase surface agitation, and increase injection?


Just depends on what's happening with the ph drop after 2.30pm. Does it drop below 6.41 or remain stable? If it remains stable it might just be a case of starting the injection time a couple of hours earlier, if it continues to drop which is what I expect is happening then you might need to increase surface agitation, and start injection time earlier.
Given you've already had issues with the fish showing stress I'd be tempted to increase surface agitation a bit and start the gas at 7.30am, then 7 etc, and do a full  co2 profile till lights out.

Obviously don't make changes to the co2 if you aren't around to monitor it.


RickyV said:


> I guess its probably best to not mess with the CO2 right now and see how plants respond from the chelated iron and Mg?


I'd get the co2 stable as a no1 priority. But sure add the extra nutrients as well.


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## RickyV (22 Nov 2022)

John q said:


> I'd get the co2 stable as a no1 priority. But sure add the extra nutrients as well.


Makes sense, I will work on getting that line more flat.


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## Yugang (22 Nov 2022)

RickyV said:


> the pH of my tapwater is 7.7


The tap water may contain CO2 (up to 50 ppm, depending where it is sourced from) and is therefore not the correct pH reference for measuring the pH drop. It is important to have the tank water first fully degassed, and take the pH reference on that.
(After each water change I take a sample of my tank water, let that stand in an open jar in the cabinet so that I can check on this, a few days later and fully degassed, if I want to)
Dialling in the CO2 injection Rate and CO2 Profiles

If you succeed to stabilise the CO2 in a 1200 l tank (without using a CO2/pH controller) within 2-3 hours you will be your CO2 suppliers best customer. The bigger the tank, the more time it takes. You would need a high CO2 injection rate (CO2 consumption, especially for such big tank) and high surface agitation/outgassing to reach the stability in a reasonable time.  A pH/CO2 controller is a game changer for this tank, and in the USA more commonly used than in Europe.


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## KirstyF (23 Nov 2022)

@Yugang is absolutely right here. Your total drop wants to be 1ph from de-gassed tank water (not tap or ‘gas on’ level) Ideally this should be by lights on, and then steady from there till lights off.

I’m using around 1kg (2.2lbs) pw on 700ltrs to achieve that, though Co2 use is hugely variable in different set ups, and my gas is on 2.5hrs before lights start (3hrs before lights are on full)


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