# Evaporation and the pH profile (ie. CO2 levels)



## JoshP12 (9 Jun 2020)

Hi everyone,

I have an ATO (auto top off) - but until then, I am curious.

I have recently lost lots of shrimps and noticed recursive behavior in my livestock after water changes. I want to be able to leave for 3 days without worrying about the tank (I have an auto doser) but this water evaporation is killing me.

After water change day (yesterday), today I noticed signs of CO2 suffocation in an Amano shrimp (unfortunately, I know the signs now ) --yesterday was the absolute healthiest I have seen all of my tank mates, absolutely no lethargy in animals and plants very healthy. I will set my ATO at that height. But for now, I noticed that about 1/2 inch to an inch of water (impacting surface agitation of course) is literally throwing my CO2 levels (or my O2: CO2 ratio) off - so I am walking a fine line.

I find it crazy the impact surface agitation has; prior to this, I removed my skimmer (just to see) and killed more shrimp  because of surface scum build up  ... so gaseous exchange is real.

I could turn down CO2, but it is stable and clearly (since I observed yesterday) is at a great level.

Misery loves company - has anyone else observed this or have any insights to share?

I am in pursuit of finding the level that I can top it off to, without killing livestock and be able to not drop my CO2 so far down from evaporation (which I also noticed on day 3 of a different top-up level my DC was way greener than usual ).

How often do you guys do it? Do you do it daily?

Josh

Oh, I should add my neons show no signs of distress - the only ones that do are the Amanos and then my otto cat's sometimes go closer to the top (which I know now is a sign -- they hover differently).

*EDIT: Or does this just not matter and I should just top it off lower and not worry?*


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## jaypeecee (9 Jun 2020)

Hi @JoshP12


JoshP12 said:


> ... so gaseous exchange is real.



It most certainly is. I wonder how many people do a pH profile and then set CO2 injection rate/timing + lights timing to suit, then find that even the thinnest layer of scum can cause CO2 concentration to rise beyond the 30 ppm 'safe limit'? If a surface skimmer gets bunged up, this may be all that it takes.

So, here's a thought - could you use your pH probe/monitor to control the ATO in some way? Or, is it a DO probe that you have?

JPC


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## Nick72 (9 Jun 2020)

I've also noticed this.

I had to do my PH Profile much closer to the minimum water level (water level on the sixth day after water change), and learn not to fill the tank too high.

If I go too high I get less agitation and higher CO2 build up.  I now fill to about an inch below the rim, I then get a further inch / inch and a half drop over the week, but this doesn't throw my C02 off too much.

Essentially I have greater agitation all week, which means higher evaporation, but low contrast between agitation from day one to seven - and I've tuned CO2 for this higher agitation.

I don't top up during the week, but I guess tank size and the volume  to surface area ratio will make this very individual for each tank.


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## JoshP12 (9 Jun 2020)

jaypeecee said:


> Hi @JoshP12
> 
> 
> It most certainly is. I wonder how many people do a pH profile and then set CO2 injection rate/timing + lights timing to suit, then find that even the thinnest layer of scum can cause CO2 concentration to rise beyond the 30 ppm 'safe limit'? If a surface skimmer gets bunged up, this may be all that it takes.
> ...



Thanks JPC! I am running a 4 day pH probe test to see if with evaporation the pH minimum actually increases. I would just set the ATO to the level that I know works well with my pH drop and that will stay consistent ... rule out more and more factors. 

I can attest to exactly that. I saw 2 Amano perish + neons gasp + otto faint one day and the only difference was the build up of surface scum -- I saved the neons and the otto. This tells me that my CO2 is at this range of dicing with death. 1 day everyone is good, the next day that happens. The only difference was scum + CO2. 

The thing that I hate about this hobby is that our mistakes cause death; it's not like cooking where I can eat my burnt food. 

Josh


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## JoshP12 (9 Jun 2020)

Nick72 said:


> I've also noticed this.
> 
> I had to do my PH Profile much closer to the minimum water level (water level on the sixth day after water change), and learn not to fill the tank too high.
> 
> ...



It makes me feel better to know that someone else has noticed and seen this.

Thanks for sharing.

EDIT: Have you noticed any adverse affects throughout the week by having decreasing CO2 levels each day? @Nick72


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## JoshP12 (9 Jun 2020)

The thing that is crazy for me (throughout this learning curve) is that my neons were unaffected, my ottos were mid range, and my amanos died. 

CO2 affects each livestock differently -- you can read this 100000 times but experiencing it and seeing it is something totally different.


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## JoshP12 (9 Jun 2020)

Quick update! 

I did remove maybe 1 cm or 2 of water from the top this morning (after I noticed this); the amano who was culvusing is back up and swimming - it took 4 hours but we are good. 

Josh


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## jaypeecee (9 Jun 2020)

JoshP12 said:


> The thing that is crazy for me (throughout this learning curve) is that my neons were unaffected, my ottos were mid range, and my amanos died.



Hi @JoshP12 

I did some digging to see if there were any scientifically-derived upper limits for CO2 toxicity on shrimp and found this:

"The highest concentration that did not induce significantly higher mortality was 23.8 mg/L of CO2".

You can read more here:

https://aquariumbreeder.com/co2-in-a-shrimp-tank/

Michael, the author of this article is very helpful. I was in touch with him a few weeks ago. You can contact him directly from the above website.

JPC


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## jaypeecee (9 Jun 2020)

Nick72 said:


> ...I guess tank size and the volume to surface area ratio will make this very individual for each tank.


Hi @Nick72 

Yes, I agree. And, in order to get optimum exchange of gases, it's the surface area to volume ratio that needs to be maximized, isn't it? Or, is it? On the one hand, we want to retain CO2 but we also want to maximize oxygenation of the tank water. Wouldn't it be better if we didn't need to rely on CO2 in the first place? It may be the best source of carbon for the plants but it's a tricky one to control and optimize. Yes/No?

JPC


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## JoshP12 (9 Jun 2020)

jaypeecee said:


> Hi @JoshP12
> 
> I did some digging to see if there were any scientifically-derived upper limits for CO2 toxicity on shrimp and found this:
> 
> ...



Thanks! That is great! I will read through to see how Amano's fair in here. 

Josh


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## sparkyweasel (9 Jun 2020)

jaypeecee said:


> And, in order to get optimum exchange of gases, it's the surface area to volume ratio that needs to be maximized, isn't it?


It's back to basics isn't it?
Old-time aquarists didn't know their phosphate levels, Ca/Mg ratios or PAR. But they knew gas exchange was important, and that surface area was important for good gas exchange. It seems to have got forgotten somewhere.


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## jaypeecee (9 Jun 2020)

Hi @JoshP12 

On the basis that "The highest concentration that did not induce significantly higher mortality was 23.8 mg/L of CO2", how does your tank stack up against this figure?

JPC


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## JoshP12 (10 Jun 2020)

jaypeecee said:


> Hi @JoshP12
> 
> On the basis that "The highest concentration that did not induce significantly higher mortality was 23.8 mg/L of CO2", how does your tank stack up against this figure?
> 
> JPC



I am not sure; clearly, I was over that amount today. A pH drop of 1.2/3ish maybe and a lime green DC; more importantly,there has been no new algae on new growth - old algae is still growing but slow and I will just trim it away as more leaves come in - and plants are healthy, so the only tell tale is the distress on the Otto cats - so whatever their max threshold is maybe knock a couple off that and that was my level.

In terms of moving forward, I decided just to top it off as @Nick72 is doing - at that level just high enough and top it off every couple days and move on to more important things to fix in the tank. When I am way, I will just have someone fill it up to the line that I leave - until the Auto Top Off gets here.

I think for the sake of this, I learned a lot and realized how much thought goes into dialing in CO2 - and how toxic the substance really is.

Josh


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## JoshP12 (10 Jun 2020)

sparkyweasel said:


> It's back to basics isn't it?
> Old-time aquarists didn't know their phosphate levels, Ca/Mg ratios or PAR. But they knew gas exchange was important, and that surface area was important for good gas exchange. It seems to have got forgotten somewhere.



A lot of basics aren't discussed.

I am relatively new to the hobby and simple things like making sure my water change water was the same as my tank water was never "taught" to me. Sure, it would've been easy if I just used tap water, did my water change regularly, did maintenance properly (which I had no clue how to do), and moved on. But the advice that I received from LFS and the hodge-podge of reading that I did didn't help (well it did, but ... I think you know what I mean).

For this reason, I am thankful for finding UKAPS; with a math/science background, I can't just follow what people "say", I truly need to understand what is happening.

I am sure it would be much easier if I just followed a design that said, buy this tank, use that output, put that output there, put that skimmer on the input, buy all your plants at tropica in those little cups, buy a doser, buy an ATO, etc etc -- but I am part thrifty too  ... and I suppose the emotional rollercoaster of this hobby keeps me in it HA.


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## jaypeecee (10 Jun 2020)

JoshP12 said:


> ...with a math/science background, I can't just follow what people "say", I truly need to understand what is happening.



Hi @JoshP12 

My sentiments entirely!

JPC


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## sparkyweasel (10 Jun 2020)

JoshP12 said:


> I am sure it would be much easier if I just followed a design that said, buy this tank, use that output, put that output there, put that skimmer on the input, buy all your plants at tropica in those little cups, buy a doser, buy an ATO, etc


That's only easier until it goes wrong. 
If you know why you are doing things you are in a better position to work out the cause of any problems.


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## dw1305 (11 Jun 2020)

Hi all, 





JoshP12 said:


> For this reason, I am thankful for finding UKAPS; with a math/science background, I can't just follow what people "say", I truly need to understand what is happening.


Yes I'd agree, it absolutely amazes me that people are willing, for example, to  use CO2 without  fully understanding the dangers and/or the chemistry involved. 

However knowledgeable, and skillful, you are sooner or later this hobby will always <"_bite you in the bottom_">,  all you can do is try and prolong the time interval to "later".

cheers Darrel


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## JoshP12 (11 Jun 2020)

dw1305 said:


> Hi all, Yes I'd agree, it absolutely amazes me that people are willing, for example, to  use CO2 without  fully understanding the dangers and/or the chemistry involved.
> 
> However knowledgeable, and skillful, you are sooner or later this hobby will always <"_bite you in the bottom_">,  all you can do is try and prolong the time interval to "later".
> 
> cheers Darrel



It's hard - several months ago I had only awed at the CO2 enriched aquariums - and all you think (when you don't know any better and are new into the hobby) is lets do it. Several hundred dollars later, you realize that learning CO2 is harder than keeping fish itself. 

The guilt of deaths is rarely discussed.

For every 100 posts on nutrients, there is 1 person who admits to gassing fish (I made this figure up). I love the idea of the pH profile as it gives some structure to learning; conversely, the notion of mastery and watching your fish requires expertise that inevitably only comes from gassing/nearly gassing everything.  🧐


Josh


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## jaypeecee (11 Jun 2020)

JoshP12 said:


> It's hard - several months ago I had only awed at the CO2 enriched aquariums - and all you think (when you don't know any better and are new into the hobby) is lets do it. Several hundred dollars later, you realize that learning CO2 is harder than keeping fish itself.



Hi @JoshP12 

I'm so full of thoughts but don't know where to begin. But, I'll make a start and hope it makes sense! If not, I'll try again.

Perhaps one of the difficulties in keeping healthy plants arises because we try to use water that is low in bicarbonates ('low' KH). As Diana Walstad* points out:

"...plants that can use bicarbonates (in addition to CO2) have an enormous advantage in alkaline water".

Apparently, half of the aquatic plants tested** (almost thirty years ago) can use bicarbonates.

I translate that to mean I may be better off using plants whose natural habitat is hard water. And I've been keeping mine in soft water. 

Food for thought?

JPC

* Ecology of the Planted Aquarium

** Madsen TV and Sand-Jensen K. 1991 Photosynthetic carbon assimilation in aquatic macrophytes. Aquat. Bot. 41: 5 - 40


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## jaypeecee (11 Jun 2020)

Sorry.....and perhaps CO2 injection isn't necessary with hard water? But we may need to keep topping up KH?

And, here's a link:

https://www.sciencedirect.com/science/article/abs/pii/0304377091900376

But, the full paper is not free.

JPC


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## dw1305 (11 Jun 2020)

Hi all, 





jaypeecee said:


> Perhaps one of the difficulties in keeping healthy plants arises because we try to use water that is low in bicarbonates ('low' KH). As Diana Walstad* points out: "...plants that can use bicarbonates (in addition to CO2) have an enormous advantage in alkaline water"............


I think part of the reasons why Diana Walstad was keen on having water with a lot of carbonate hardness was that, when she wrote <"Ecology of the Planted Aquarium">, she wasn't advocating a filter, or water changes, so she needed a <"reservoir of hardness to counter "old tank syndrome".>

I think subsequently she revised her initial suggestion to include both <"water movement and water changes">. 





jaypeecee said:


> ......Apparently, half of the aquatic plants tested** (almost thirty years ago) can use bicarbonates. I translate that to mean I may be better off using plants whose natural habitat is hard water.


This is back to our old friend the <"CO2 ~ pH ~CO2 equilibrium and Total Inorganic Carbon (TIC)">, but whatever form that TIC takes the plants <"will always use it as CO2">.

 I've always used <"relatively soft rain water"> and I think the consensus of opinion would be that <"low dKH allows you to grow a wider range of plants">.

cheers Darrel


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## jaypeecee (11 Jun 2020)

Hi @dw1305


dw1305 said:


> I think part of the reasons why Diana Walstad was keen on having water with a lot of carbonate hardness was that, when she wrote <"Ecology of the Planted Aquarium">, she wasn't advocating a filter, or water changes, so she needed a <"reservoir of hardness to counter "old tank syndrome".>



I have the third edition (2012) of Diana Walstad's book, this being the latest edition. But, I'm not clear why the quote I gave from her book is now invalid. And I don't see the relevant connection with the need for a 'reservoir of hardness'. I bought Diana Walstad's book on your recommendation. I'm obviously missing something here. Would you mind explaining this for me, please, Darrel? I really want to understand this.

JPC


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## sparkyweasel (11 Jun 2020)

jaypeecee said:


> Sorry.....and perhaps CO2 injection isn't necessary with hard water?


It's not _necessary _at all 
It can give faster growth. And more pruning and maintenance. 
And it can help to grow plants fully submerged when the species would naturally grow emergent, or periodically alternating between submerged and emersed.
It's easy enough to let your plants grow naturally, you just have to accept the limitations.


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## jaypeecee (11 Jun 2020)

Hi @dw1305 

I can just about follow Clive's post to which you referred. But, the results from one of Diana Walstad's own experiments clearly demonstrate that some plants do grow much better in alkaline hardwater. She shows a photo in her book where she had Vallisneria spiralis grown under two different conditions. One was hardwater with alkaline desert soil, the other was in softwater with acidic peat substrate. The first of these plants grew very well whilst the second plant disintegrated. Figure VII-3 in her book refers. Is there, perhaps, some other explanation for her observations other than water hardness? Is the difference in pH the more likely explanation? I don't know but I would welcome any comments from anyone on this.

And, if people reading this are thinking that it is just science for science's sake, no, it isn't. If there's a better way of delivering carbon to our plants than using CO2, just think of all the advantages that could potentially bring.

JPC


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## jaypeecee (11 Jun 2020)

Hi @sparkyweasel


sparkyweasel said:


> It's not _necessary _at all  It can give faster growth. And more pruning and maintenance.  And it can help to grow plants fully submerged when the species would naturally grow emergent, or periodically alternating between submerged and emersed. It's easy enough to let your plants grow naturally, you just have to accept the limitations.



Thanks ever so much for the feedback. May I ask what the limitations are? Do I need to ensure that the plants I choose are suitable for hard or soft water?

TIA.

JPC


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## dw1305 (11 Jun 2020)

Hi all, 





jaypeecee said:


> And I don't see the relevant connection with the need for a 'reservoir of hardness'.


Diana Walstad had to use calcareous soil and hard water in her tanks to provide the carbonate hardness  needed for nitrification. Because you didn't change any water that hardness wasn't replenished by water changes. Because she had hard water the pH would always be above pH7, and the TIC would always  be in the form of HCO3-,.

She had to use plants that could use HCO3- as their carbon source, because there wasn't ever any free CO2 available.





jaypeecee said:


> I bought Diana Walstad's book on your recommendation.


I recommend every-one buys a copy, there still hasn't been anything written of  similar scope.





jaypeecee said:


> one of Diana Walstad's own experiments clearly demonstrate that some plants do grow much better in alkaline hardwater


They do, <"_Vallisneria  _doesn't like life in  the tanks">, but grows well in our tap water (about 17dKH & 17 dGH). It maybe an <"iron toxicity effect etc.">, rather than  directly  related to pH/dKH.


jaypeecee said:


> Do I need to ensure that the plants I choose are suitable for hard or soft water?


Most  "easy" plants won't care either way.

cheers Darrel


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## sparkyweasel (11 Jun 2020)

Yes, or those that are not fussy about hardness.
Any that are classed by suppliers as needing high CO2 will probably struggle without injection, unless they have access to the air.
For example, I like Japanese Rush, but it does not do well completely submerged, some say you can't grow it in a tank. But if you let the tops of the leaves stick up above the surface they are fine.


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## jaypeecee (11 Jun 2020)

Hi @dw1305


dw1305 said:


> Because you didn't change any water that hardness wasn't replenished by water changes.



I don't believe I said anything about water changes, Darrel. This thread refers to a tank owned by @JoshP12.

JPC


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## dw1305 (11 Jun 2020)

Hi all, 





jaypeecee said:


> I don't believe I said that, Darrel.


No, Diana Walstad was the person who originally  didn't change any water, as far as I know everybody else does.

cheers Darrel


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## jaypeecee (11 Jun 2020)

Hi @dw1305


dw1305 said:


> No, Diana Walstad was the person who originally didn't change any water, as far as I know everybody else does.



Perhaps you meant to say "Because you she didn't change any water that hardness wasn't replenished by water changes"? See post #26.

JPC


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## JoshP12 (11 Jun 2020)

Hi all,

Lots of good stuff here!!!

I also have her book, and I am thinking of cracking it open and giving it a second read, having learned a lot since my first gander.

Josh


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## hypnogogia (13 Jun 2020)

dw1305 said:


> They do, <"_Vallisneria _doesn't like life in the tanks">, but grows well in our tap water (about 17dKH & 17 dGH). It maybe an <"iron toxicity effect etc.">, rather than directly related to pH/dKH.


Interesting.  I had Vallis and it grew like a weed.  My water is 4.5dKh, and 7Gh.  It got too much and eventually I too, it all out as it constantly interfere pd and smothered other plants. Would it have been more rampant in harder water?


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