# Plants using bicarbonates for photosynthesis?



## Ullalaaqua (26 Mar 2021)

Can’t keep this in anymore so here you go:
If you’ve  read the journal about my nanotank you’ll know I got my rotalas to pearl without adding CO2.  So I started to dig around after a friend of mine gave me some useful tips.


At this point I knew the reaktion behind those bubbles had something to do with bicarbonates (HCO − 3) and more spesifically the carbon (C) inside those carbonates.  
Now I’m not a scientist and not really good understanding the complexity of waterchemistry and aquatic plant nutrition so I continued with a hunch here.

My hunch was that since I had no pressurized CO2 in the tank, no hardscape affecting the kh levels, the reaktion had to have something to do with the potassium (K) fertilizers - and watercare products that increase kh value.

So I made an experiment with ADA Brighty K which, if I have understood correctly, is potassiumcarbonate (K2CO3). After couple of hours I got bubbles again.






Today I tried the same with ARKA Microbelift Plants K that should be potassiumcarbonate too, but still no reaktion. So I read a bit more of 
the study from Kaj Sand-Jensen (https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.12812). Turns out, the ph has to be 7 or more. Yesterday I added some tapwater (ph 8) to the tank to replase the evaporated water at the same time I dosed K...  

So, if there is no bubbles when I get out of work, I’ll add some tapwater in it 😁

Would love to hear your thoughts about this! Especially from the ones who know a bit more about aquaticplants and waterchemistry. Am I even close with my hunch?


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## Ullalaaqua (26 Mar 2021)

I can’t edit this for some reason... But there was one photo missing from the first pearling earlier this week...
So here is a photo from that


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## Zeus. (26 Mar 2021)

Pearling can occur for few reasons
When the water is saturated with O2 and the water next to the leaves is unable to dissolve any more O2 bubbles form.
When water is saturated with gases esp after a Water Change (WC) these gases can form on plants, hardscape and tank.
After a WC esp in a non injected CO2 tank the extra CO2 in the tap water can give the plants a little edge with the extra CO2 and Photosynthesise a little faster and produce O2 a little faster, there are numerous reports of faster growth after WC which support the theory.
If plants are pearling soon after lights on and there hasn't been a WC I would be looking at the flow rate in the tank, as it would suggest to me that it might be inadequate.
If the light intensity is too high for the plants CO2 levels they will pearl, then get pin holes, then melt.

Although pearling can be great to see esp at first, it is a warning that you may be pushing the plants too hard with light intensity, so proceed with caution.

Although  bicarbonates are used/added to tanks to increase the kH  in tanks, which does enable folk to control the CO2 levels better/safer when injecting CO2 in tanks when users are using RO water. For most folk using tap water there is no need to add them, as there tap water supplies ample. Not sure what your water has in Finland - might be worth checking with your water supplier and you can normally find this online.


Ullalaaqua said:


> ADA Brighty K which, if I have understood correctly, is potassiumcarbonate (K2CO3).






Sorry you have been mis-informed. ADA do have some amazing products which are not cheap, but their fert line up is not one of them - ferts are ferts and plants do care which you use and ADA ferts are so over priced it is ridiculous IMO


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## Ullalaaqua (26 Mar 2021)

Zeus. said:


> Pearling can occur for few reasons
> When the water is saturated with O2 and the water next to the leaves is unable to dissolve any more O2 bubbles form.
> When water is saturated with gases esp after a Water Change (WC) these gases can form on plants, hardscape and tank.
> After a WC esp in a non injected CO2 tank the extra CO2 in the tap water can give the plants a little edge with the extra CO2 and Photosynthesise a little faster and produce O2 a little faster, there are numerous reports of faster growth after WC which support the theory.
> ...


Yes but I haven’t used this.... I used ADA Brighty K. Neutral does not affect kh values but the Brighty K does. And what comes for the other factors you listed, i’m aware of them, but none does seem to apply here. So this can’t be O2 related. Our tap water is really soft here. The kh and Gh are around 2-3. Ph in the other hand is 8.


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## Ullalaaqua (26 Mar 2021)

Zeus. said:


> If plants are pearling soon after lights on and there hasn't been a WC I would be looking at the flow rate in the tank, as it would suggest to me that it might be inadequate.
> If the light intensity is too high for the plants CO2 levels they will pearl, then get pin holes, then melt.


This is the other thing. I’ve seen those plants pearl 2 times now. First time the water change had been in the previous day and plants started to pearl couple of hours after lights went on. Yesterday about 2-3 hours too and I added more water to the tank.


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## Zeus. (26 Mar 2021)

Ullalaaqua said:


> but the Brighty K does



I stand corrected  (followed the wrong link for the product ), however the same goes the the value of the product, making your own with some potassium carbonate would work out much cheaper.

Have you tried just adding the tap water to see if you get the same affect?

If there you pics of your plants they do look good and great colours


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## John q (26 Mar 2021)

Some fantastic looking rotala there.

Maybe I've got the wrong tank here but did these  plants start off with added co2? If so then maybe they've built up a store of carbon and are using that up hence the pearling.

If these have indeed completely grown in low tech then I take my hat off to you.

Edit: just seen you haven't used co2 for 3 months.


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## Ullalaaqua (26 Mar 2021)

Zeus. said:


> I stand corrected  (followed the wrong link for the product ), however the same goes the the value of the product, making your own with some potassium carbonate would work out much cheaper.
> 
> Have you tried just adding the tap water to see if you get the same affect?
> 
> If there you pics of your plants they do look good and great colours


Yes the photos are from the tank in question 😄
Thanks.

I have added just water without dosing and this has never happened  unless there was a waterchange just before.  Now it didn’t happen with ARKAs K so just a hunch: The other is potassium bicarbonate and other potassiumcarbonate. Or I didn’t add water enough to rise ph to 7....

About ferts, I don’t see the point making my own mix since I don’t use EI method when dosing (my other tanks are with CO2). I’m more of a lean doser  This nano is only 22l anyway, so I can experiment with it easily

I tested the tap water myself and I also get the parameters from the water supplier. They show the same reading normally. Only thing that differs sometimes is the kh from the tap water. Sometimes it’s 1 and other times 3. Don’t know if it matters much...


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## Ullalaaqua (26 Mar 2021)

John q said:


> Some fantastic looking rotala there.
> 
> Maybe I've got the wrong tank here but did these  plants start off with added co2? If so then maybe they've built up a store of carbon and are using that up hence the pearling.
> 
> ...


Yes this tank had 2 weeks of CO2 injection in January and now we are at 3+ months without. So not really shure this could be the case. And if it was so, shouldn’t they be pearling in daily basis?


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## jaypeecee (26 Mar 2021)

Hi @Ullalaaqua 

When people refer to plants 'pearling', they are referring to oxygen (O2) bubbles forming. But, I'm wondering if the bubbles you are seeing are carbon dioxide (CO2) bubbles instead. The addition of potassium carbonate and/or potassium bicarbonate to your tank water may be producing CO2, which is simply clinging to surfaces that are not smooth. I may be way off the mark and will give this some more thought.

JPC


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## jaypeecee (26 Mar 2021)

Hi @Ullalaaqua 

There seems to be two sources of potassium (K) here:

Brighty Neutral K (derived from potassium chloride, KCl) and...
Brighty K which is 'strongly alkaline'. But, the label says nothing about its composition - unless I've missed something.

However, you do say:



Ullalaaqua said:


> So I made an experiment with ADA Brighty K which, if I have understood correctly, is potassiumcarbonate (K2CO3).


 
Where did you get the information that Brighty K contains potassium carbonate?

JPC


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## John q (26 Mar 2021)

Ullalaaqua said:


> Yes this tank had 2 weeks of CO2 injection in January and now we are at 3+ months without. So not really shure this could be the case. And if it was so, shouldn’t they be pearling in daily basis?



Apologies, I'd thought that co2 had only been stopped a few days ago.


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## jaypeecee (26 Mar 2021)

Hi @Ullalaaqua 



jaypeecee said:


> Where did you get the information that Brighty K contains potassium carbonate?



I just checked the ADA website and, indeed, Brighty K is "derived from Potassium Carbonate". Here's a link:



			https://www.adana.co.jp/en/contents/support/liquid/manuals/BRIGHTY_K_Label.pdf
		


JPC


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## Andy Pierce (26 Mar 2021)

If we take the label at its word, Brighty K is potassium oxide (K2O).  K2O can be derived from potassium carbonate (K2CO3)  by thermal decomposition but isn't the same as potassium carbonate.  Adding K2O to water causes an immediate reaction (K2O + H2O → 2KOH) where the KOH dissociates into K+ (this is the potassium fertiliser component) and OH- which is the hydroxide anion, a very powerful base "strongly alkaline" (will raise pH) just as the label indicates.  This is probably what Brighty K is... a solution of potassium hydroxide, whereas 'Neutral K' seems to be a solution of potassium chloride.

What happens to the hydroxide?  You're injecting CO2 (and there is CO2 in the air) which will react with the hydroxide to form bicarbonate.  Overall:  KOH + CO2 →KHCO3.  So you lose a little of your CO2, the pH you raised with the hydroxide comes back down (as the label states), and you increase the carbonate hardness (dKH) of your tank.  More info on the reaction:





						What are the products of KOH(s) + CO_2(g)? | Socratic
					

"KOH"_text((aq]) + "CO"_text(2(g]) -> "KHCO"_text(3(aq]) Potassium hydroxide, "KOH", will react with carbon dioxide, "CO"_2, to form potassium bicarbonate, "KHCO"_3, and water. The balanced chemical equation for this reaction looks like this "KOH"_text((aq]) + "CO"_text(2(g]) ->...




					socratic.org
				




This leaves open the question of whether you actually *want* to increase the carbonate hardness of your tank while you're adding potassium...


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## Zeus. (26 Mar 2021)

Andy Pierce said:


> If we take the label at its word, Brighty K is potassium oxide (K2O).


However the label says



'Derived from Potassium Carbonate' , its the Analysis that throw you as they use K2O - which is classic misdirection making it harder to clone the product, we worked out the ppm of K2O then worked out the corresponding ppm of K, once we had the K ppm and using K2CO3 we worked out ppm CO3 then the  kH. Once we have the CO3 ppm or/and kH we have the clone

Big edit- made error in earlier post ( was watching TV and doing the mods to IFC )-
And the cost of making a clone with details



so same dose as ADA Brighty K




Interesting to see it adds  approx 0.5kH a week at ADA dose
and the shocking price comparison
We had overlooked the fact ADA use K2CO3 when doing the ferts clones, so glad I found this out as that was a little oversight - in our defence we did have quite a bit to do. We have a new update due to the IFC Calculator and we might be able to get this on the next update @Hanuman


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## jaypeecee (26 Mar 2021)

Hi @Andy Pierce 

So, what are the bubbles forming on the plants? Is it O2 or CO2?

TIA.

JPC


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## Zeus. (26 Mar 2021)

Made error in last post, which I spotted when checking maths- have updated post


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## Andy Pierce (27 Mar 2021)

jaypeecee said:


> Hi @Andy Pierce
> 
> So, what are the bubbles forming on the plants? Is it O2 or CO2?
> 
> ...


The classic test would be to collect the bubbles in a water-filled upside-down test tube, then add a glowing splint.  If it bursts into flame it's O2; if it goes out it's CO2.  If it explodes, it's H2.


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## JoshP12 (27 Mar 2021)

Hi all,



Ullalaaqua said:


> My hunch was that since I had no pressurized CO2 in the tank, no hardscape affecting the kh levels, the reaktion had to have something to do with the potassium (K) fertilizers - and watercare products that increase kh value.


1) Role of Potassium in Carbon Dioxide Assimilation in Medicago sativa L ... it doesn't influence Rub, PSI, PSII ... so what does it influence?
2) Effects of potassium supply on limitations of photosynthesis by mesophyll diffusion conductance in Carya cathayensis  Potassium (K) influences the photosynthesis process in a number of ways; however, the mechanisms underlying the photosynthetic response to differences in K supply are not well understood.

Those papers are for non-aquatic plants and have access to atmospheric CO2.

It gives us a starting point - *Perhaps potassium is highly influential in photosynthesis, in particular, in the activation of enzymes/reaction channels required.  *No coincidence why it is the backbone to seachem and ADA system.  In my mind, potassium is a driver of photosynthesis.

Rotala grows in low KH water and I would be pleasantly surprised if it has a mechanism (evolutionary adaptation) to utilize carbonates as say vals and/or cryts.

*A question:* How much of that growth has happened over the past 3 months? You can see some thinning on some older leaves but I do not know how old they are. Did they change into this state or just normal changing of growth?

There is a thought that "ideal" KH gives rise to "more efficient" CO2 acquisition so less does more. Perhaps because Rubisco doesn't work as well - no clue. Your tap water has low KH despite having higher pH ... so that "increase" will be temporarily.

Another piece to note is your surface agitation is low (from the photos I saw) and so any CO2 released from bacteria and/or respiration can be utilized ... if it doesn't get offgassed and the acquisition mechanism is more efficient, then a recipe for success!* Your bacteria are your CO2 injection.

Notice: *Staghorn after the observation of pearls? Pearls after potassium? The balance you had was perhaps shifted out by the addition of K ... throwing nutrient demand off balance ... allowing staghorn to take advantage?


Josh


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## sparkyweasel (27 Mar 2021)

There is a convention in ferilisers (and some other industrial chemicals) to express the amount of potassium in terms of how much K2O would give the same amount of potassium as is actually present although it may have come from other compounds, eg; K2CO3 or whatever.


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## Hanuman (27 Mar 2021)

Zeus. said:


> We have a new update due to the IFC Calculator and we might be able to get this on the next update @Hanuman


Yes the update is ready, just need some time to sanitize the file to make it user-ready and double check a few things because there has been some non-trivial changes. I have added the dKH of ADA Brighty K.


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## Ullalaaqua (27 Mar 2021)

Andy Pierce said:


> If we take the label at its word, Brighty K is potassium oxide (K2O).  K2O can be derived from potassium carbonate (K2CO3)  by thermal decomposition but isn't the same as potassium carbonate.  Adding K2O to water causes an immediate reaction (K2O + H2O → 2KOH) where the KOH dissociates into K+ (this is the potassium fertiliser component) and OH- which is the hydroxide anion, a very powerful base "strongly alkaline" (will raise pH) just as the label indicates.  This is probably what Brighty K is... a solution of potassium hydroxide, whereas 'Neutral K' seems to be a solution of potassium chloride.
> 
> What happens to the hydroxide?  You're injecting CO2 (and there is CO2 in the air) which will react with the hydroxide to form bicarbonate.  Overall:  KOH + CO2 →KHCO3.  So you lose a little of your CO2, the pH you raised with the hydroxide comes back down (as the label states), and you increase the carbonate hardness (dKH) of your tank.  More info on the reaction:
> 
> ...


Thank you for the reply! This was the closest answer to the thing I’m trying to ask 😄

My point is not wanting to increase the carbonate hardness but to understand the chemical reaction behind this possible photosynthesis with bicarbonates and if these fertilizers that rise kh (for examble ADA Brighty K) could have been the thing that made that strong photosynthesis happen in my lowtech tank in the first place.

Why I want to know? I’m just curious about stuff like this 😁


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## Ullalaaqua (27 Mar 2021)

JoshP12 said:


> Hi all,
> 
> 
> 1) Role of Potassium in Carbon Dioxide Assimilation in Medicago sativa L ... it doesn't influence Rub, PSI, PSII ... so what does it influence?
> ...


Thank you! More pieces to the buzzle 🤩

Staghorn: has been a ”problem” in this tank. I managed to get it under control, but not complitely gone.  I just had Crystal shrimp shrimplets, so I’ve been extra careful with too sudden changes even when experimenting with this   And I haven’t done spot treatment to the algae after I noticed the shrimplets eighter.
So the Staghorn has been there before I noticed pearling. Pearling happened first time after adding potassium that I know raise kh (I swiched from ADA Neutral Brighty K to ADA Brighty K.

To your question: after I stopped adding CO2 the plants came alive. Growth is slower than with CO2, but plants are stronger and fuller somehow.  I’ve trimmed the rotalas once in this time.


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## Wookii (27 Mar 2021)

Zeus. said:


> However the label says
> View attachment 165830
> 'Derived from Potassium Carbonate' , its the Analysis that throw you as they use K2O - which is classic misdirection making it harder to clone the product, we worked out the ppm of K2O then worked out the corresponding ppm of K, once we had the K ppm and using K2CO3 we worked out ppm CO3 then the  kH. Once we have the CO3 ppm or/and kH we have the clone
> 
> ...



Just incredible - I know ADA ferts are overpriced, but I didn’t realise Brighty K is just a very dilute K2CO3 based KH booster. That’s daylight robbery.

I wonder why they choose to use that rather than K2SO4. If memory serves, Brighty K is ADA’s first stage fert in their pre-prescribed regime, so is it perhaps to help buffer the declining KH due the organic acids released from the Amazonia?


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## Oldguy (27 Mar 2021)

sparkyweasel said:


> There is a convention in ferilisers


Total agree with @ sparkyweasel . The convention with fertilizes is to show key ingredients in a standard format so that one brand can be compared to another.
Potassium is not there as K2O and Phosphorus is not  there as P2O5, both far too reactive. However it does enable comparisons to be made and actual formulations to be hidden.


Ullalaaqua said:


> had something to do with bicarbonates (HCO − 3)


Lovely pics @ Ullaaaqua.

Have used sodium bicarbonate solution and a desk lamp on Canadian Pondweed to demonstrate photosynthesis, easy to collect oxygen but hard on the plant. 

Potassium bicarbonate would be a better choice than the carbonate, less effect on pH and it dissociates to the hydrogen carbonate ion which some plants use as a carbon source.
These plants are hard-water species because in natural waters the bicarbonate will be from calcium which often forms a white deposit on the plant leaves.

I mix my own aquarium ferts, so cheap compared with shop products and I like the nostalgia of having a 'chemistry set' so unfortunately cannot comment on over the counter products.

Happy fish tanks.


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## Sammy Islam (27 Mar 2021)

Wookii said:


> Just incredible - I know ADA ferts are overpriced, but I didn’t realise Brighty K is just a very dilute K2CO3 based KH booster. That’s daylight robbery.
> 
> I wonder why they choose to use that rather than K2SO4. If memory serves, Brighty K is ADA’s first stage fert in their pre-prescribed regime, so is it perhaps to help buffer the declining KH due the organic acids released from the Amazonia?



K2SO4 has lower solubility level than the others i think? Could also be a depleting KH thing as you have suggested.


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## Zeus. (27 Mar 2021)

sparkyweasel said:


> There is a convention in ferilisers (and some other industrial chemicals) to express the amount of potassium in terms of how much K2O would give the same amount of potassium as is actually present although it may have come from other compounds, eg; K2CO3 or whatever.



Thats makes some sense esp having come across a K2O% for many products when doing the IFC calculator, suppose its just like many quote N% in the analysis when the Nitrogen is a compound. We have done a similar approach for the comparison of Ammonium and Urea salts so we can compare the potential NO3 ppms for a given dose, obviously the biological pathways haven't taken place when we dose the salt/fert and we are assuming they will with a mature tank/filter. With Ammonium and Urea fert dosing I am a fan of dosing very lean doses very frequently (100 times a week with AIO) to allow these pathways to take place and migrate the potential toxic effects of using Ammonium/Urea as a source of Nitrogen.



Sammy Islam said:


> K2SO4 has lower solubility level than the others i think?


K2CO3 solubility is pretty good at 20 degrees from the data we have on the IFC Calculator


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## dw1305 (27 Mar 2021)

Hi all, 


jaypeecee said:


> So, what are the bubbles forming on the plants? Is it O2 or CO2?


They are probably oxygen. This (school) <"photosynthesis practical"> works much more efficiently with added KHCO3 (or <"NaHCO3">).

cheers Darrel


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## Zeus. (27 Mar 2021)

dw1305 said:


> Hi all,
> 
> They are probably oxygen. This (school) <"photosynthesis practical"> works much more efficiently with added KHCO3 (or <"NaHCO3">).
> 
> cheers Darrel



Yes, even though it was a very basic experiment the after about 10mins the explanation about the aerenchyma as the transport vessels for gases from plant to root and the fact they said adding xCO3 to the water helps increase the O2 produced for the students. Does strongly suggest adding CO3 helps increase O2 production


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## tiger15 (27 Mar 2021)

How much light intensity do you have?  Intense light will triggers pearling of O2 with or without CO2 injection.  I rarely observed pealing in my high tech medium light tank, but pearling occurs in my zero tech shrimp bowl every afternoon when sunlight hit.  CO2 is stripped to 0.1 ppm by photosynthesis at the peak of sunlight, yet the growth rate of Lugwidgia is near zero due to CO2 limitation.

I don’t think you have any hardwarer plant such as Vals that is capable of splitting carbonate,  and splitting carbonate is an inter cellular reaction and you won’t observe CO2 pearling but precipitation of white calcium mineral.  CO2 has high solubility and pearling CO2 is much rarer than  pearling O2, CH4 and N2.

Staghorn belongs to red algae as BBA, and can be eliminated effectively by excel and/or peroxide.  But since you have crystal shrimp reproducing, dosing either can impact their reproduction, though adult shrimp can tolerate excel within recommended dosage.   I have dosed excel many times to my cherry shrimp bowl with no death observed,   The safest way to treat staghorn is to spray peroxide to exposed plants when you lower the water level during water change.


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## Ullalaaqua (27 Mar 2021)

@tiger15 
I don’t have the exact PAR numbers to give you about the light intensity. But they are at 100% around 10 hours per day. The light is ONF flat nano.  

Good point about the hardwater plants. This is why I was so buzzled to see rotala pearling and after my friend gave me a tip about plants using bicarbonates for photosynthesis I wanted to look into that.  There has been really good information in this thread about all the posibilities and then some 😄 This forum is amazing!

The Staghorn is a pain and I had good results with spot dosing excel before I noticed one of the crystals carrying eggs. So I haven’t done anything about it since. Some say that NPK dosing would help getting rid of it, but I desided to just try and focus on the plant health and keeping the tank balanced as it is. I still have the option to put CO2 back and running. But the crystals seem so much healthier without it and the tank seems well balanced recardless the Staghorn.
Maybe I’ll just let the shrimplets grow and see if regular maintenance and dosing will eventually make Staghorn go away. You think carbonates give red algaes more boost on growing? I have a faint memory they might like higher kh levels more.


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## Geoffrey Rea (28 Mar 2021)

Ullalaaqua said:


> I don’t have the exact PAR numbers to give you about the light intensity. But they are at 100% around 10 hours per day. The light is ONF flat nano.







😉


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## Ullalaaqua (28 Mar 2021)

@Geoffrey Rea
Haha thanks 😆
Now I just have to convert the inches to cm


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## tiger15 (31 Mar 2021)

Ullalaaqua said:


> @Geoffrey Rea
> Haha thanks 😆
> Now I just have to convert the inches to cm


Have you found out your light intensity.  I bet you have high light judging from the vivid color of your Rotala.  Mine don’t get as red as yours under medium light.


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