# Experiment: pH swings with Vallisneria



## Manthalynn (Aug 23, 2008)

*Quick and dirty explanation:* *I learned that Vals can pull "stuff" from the water (carbonates) if they don't have enough CO2 they can pull from to carry out photosynthesis. In pulling the "stuff" from the water, they cause pH swings. I'm interested to see how big these swings are.*

Longer explanation below...sorry for the painful, blow-by-blow detail.

While researching plants, I discovered this information about Vals.



> "They [Vals] also do well in hard water and under bright light will strip CO2 from the KH molecule, causing biogenetic de-calcification."


Aquabotanic.

It further defines "biogenetic de-calcification".


> "When there is a carbon dioxide deficiencey in the water, plants can derive CO2 from the hardening constituents of the carbonate hardness. First they split the hydrogen carbonates into CO2 and carbonates. This causes the pH to rise about one step and the largely insoluable carbonates precipitate and form rough deposits on the leaves and substrate. Some plants such as Vallisneria can even destroy the carbonates and obtain CO2 from them. This raises the pH again by another step. Biogenic decalcification thus causes the water to be 10 to 100 times more alkaline than it was previous. In the dark, the process reverses and the pH drops considerably. Thus these continous large pH swings can pose a significant risk to the well being of fish and animals. The solution is to add enough CO2 to the water and have a significant carbonate level to act as a buffer."


I have ridiculously hard water and high pH (8.2-8.4) and a planted tank that is largely composed of Vals. I do not dose with CO2, so I'm assuming my plants are running on a deficiency. I am curious as to how much of a pH swing my plants are causing in my tank. My water may be so insanely hard that the few plants I have doesn't swing the pH very much, but I'm interested to try the following experiment (which in no way is exactly scientific since I have too many variables and no control group). 

I plan on testing my water pH right before turning on my light (hence, it having been darkest longest) so my pH should be the lowest it's going to be during the day (assuming these plants are C3 plants that carry out photosynthesis during the day). Then I will test the pH at the end of the day, after the light has been on and the pH should be the highest because the Calvin cycle is stripping the carbonates from the water to replace the missing atmospheric CO2.

I have a newly cycled 29gal tank (it's fairly stable now so we'll call it good enough for this non-scientific experiment) that has a substrate of Eco Complete. It has one large piece of driftwood that has been in there for several weeks and doesn't appear to leach any tannic acid (it surprisingly doesn't change the water color so I'm not worried about catching a pocket of acidic water that will skew my results). It has two swordtail fish, 4 mollies, 6 neon tetras, and 5 ghost shrimp. I keep the temp around 80degrees F.

As for plants, I have 10 Vals (either Contortion or Corksrew...can't tell, they look alike). I also have one Anubias nana, two clumps of Dwarf Val, a clump of baby tears, 3 small Amazon swords, 2 dwarf onions, and a green leaf crypt of some sort. (I'll post a photo soon...) My lighting is 1 65W Power Compact strip light ( 1 65 watt 6700K straight pin base compact flourescent lamp). For filtration I have a Whisper 30 (145 gph) and an Aquaclear 50 (gph 200gph). I also have a Fusion 200 airpump powering a 10" air bubble wand/curtain. And a Stealth 200W submersible heater.

As I said, I plan on testing the pH right before turning the light on in the morning and then just before turning it on in the evening. I will record the results for several days, just to make sure one day doesn't throw off the numbers. Then I'll plot these on a graph and see if there were any pH swings.

*Questions:* 
1)How long should I set the timer to leave the light on for? An equal 12 on and 12 off (I'm expecting an algae bloom if I do that... but that's ok if it's all in the name of science!) 

2) I heard mention of a pH "pen" that is more accurate than strips or droppers. I currently use API's high pH dropper i 5ml of water. I can never tell exactly what color it is, so I'm not sure if it's very accurate. Does any one recommend a good and quick pH test device? I'm willing to spend around $20 on this (I'll use it for more than just this experiment)

3) Would you be willing to donate money for me to see a therapist because I'm clearly neurotic for wanting to do this! (Just kidding!)

Thanks in advance for any input, suggestions, or questions!


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## Manthalynn (Aug 23, 2008)

Photos of said tank. Sorry they're so crummy, my camera is on it's last legs.

I have one of the Aquaclear intake tubes floating around in the tank in case you're wondering what that is. I know, silly. I took it off to clean the tube and forgot to put it back on. There's still one on the filter, though.


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## jones57742 (Sep 8, 2007)

Sam:

You are really :chair: :chair: :chair:

Just humor of course but I did have to read your post several times in order to understand the particulars as well as generalities.



Manthalynn said:


> Then I'll plot these on a graph and see if there was any pH swings.


were My head feels better.




Manthalynn said:


> ]1)How long should I set the timer to leave the light on for? An equal 12 on and 12 off (I'm expecting an algae bloom if I do that... but that's ok if it's all in the name of science!)


IMHO 10 hours.

Only the equator receives 12 hours of daily sunlight but due to refraction ...




Manthalynn said:


> 2) I heard mention of a pH "pen" that is more accurate than strips or droppers. I currently use API's high pH dropper i 5ml of water. I can never tell exactly what color it is, so I'm not sure if it's very accurate. Does any one recommend a good and quick pH test device? I'm willing to spend around $20 on this (I'll use it for more than just this experiment)


If you can find one which produces identical results subsequent to rinsing in RO water and the results are identical to a liquid test kit please publish and I will purchase one.




Manthalynn said:


> 3) Would you be willing to donate money for me to see a therapist because I'm clearly neurotic for wanting to do this! (Just kidding!)


No.

TR


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## emc7 (Jul 23, 2005)

IMO all pH meters are as only good as their calibration. Unfortuaty, good new electronic, temperature-correcting, pre-calibrated meters are more than $20 now. I think I paid about $40 and it now sells for $60 or $80. Mine worked well for over a year and now reads high. I can fix it with the press of a button as soon as I find my calibration solutions or order new ones. When you have $ to spare (if you ever do), the new ones that do temp, TDS & pH all-in-one are cool. Even liquid tests should be run on a standard once in a while to verify they still read true. I don't claim they are more accurate than liquids. I think they do tenths, plus or minus one-tenth. The real accurate pH meters are electrodes like the school labs have. You can buy them from the salt water dealers for hundreds of dollars. Of course, then you have to calibrate them.

Fish are therapy, and also expensive.

http://cgi.ebay.com/Pen-Type-pH-Met...14&_trkparms=72:1205|66:2|65:12|39:1|240:1318 

This isn't a brand I know, but this is what to look for. Its quicker to test and more reproducable than reading colors.


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## Manthalynn (Aug 23, 2008)

jones57742 said:


> Just humor of course but I did have to read your post several times in order to understand the particulars as well as generalities.


Ron, I edited my post and added a "quick and dirty" explanation at the top. Brevity has NEVER been my strong suit. Perhaps I should have spent more time formulating my post into a clearer report format...

And thanks for the grammar correction! I don't know what I was thinking. Probably wasn't...



> IMHO 10 hours.


10 sounds good. Thanks for the recommendation.


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## Manthalynn (Aug 23, 2008)

emc7 said:


> The real accurate pH meters are electrodes like the school labs have.


I remember seeing those at work at our greenhouse...



> Fish are therapy, and also expensive.


 I second that! I actually decompress at night by sitting in my glider rocker watching my fish tanks. Thanks for helping me justify it! (Hmm...justify sounds like making up a fake reason...it's not a fake one but a good one! Some people buy lights for Seasonal Affective Disorder, some people buy fish tanks!)



> http://cgi.ebay.com/Pen-Type-pH-Met...14&_trkparms=72:1205|66:2|65:12|39:1|240:1318
> 
> This isn't a brand I know, but this is what to look for. Its quicker to test and more reproducable than reading colors.


Actually, that one was new. $27 US actually isn't that expensive! I really hate trying to judge the color on my tester kits and I question my objectiveness. I'll have to seriously consider that link. 

Thank you for your suggestions!


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## Manthalynn (Aug 23, 2008)

jones57742 said:


> IMHO 10 hours.
> 
> Only the equator receives 12 hours of daily sunlight but due to refraction ...


So I've been thinking about your post as I've had to put my experiment on hold during dead week and now finals week (almost done! 36 more hours until my Botany final!!!)

I realized that yes, only the equator recieves 12 hours of daylight year round. But each hemisphere experiences over 12 hours of light at some point in the year. And some plants are day-length sensitive. (Delphinium/Larkspur are long day - they flower when they receive 16+ hours of light per day; Mums are short day...not sure what the critical photo period is for them...)

So if the particular plants I have in my tank ARE day-length sensitive, I am putting them in a state of perpetual "winter". Which is fine if winter growing processes is what I'm aiming for. 

Then again, this is a TROPICAL tank, and most tropical plants are day-length neutral (which means they don't care about the length of day since where's they're native to, there isn't much length variation...). And I've noticed that if I have the lights on for too long, Algae starts to grow and that's never good...

Thanks again for trudging through my plan and sucessfully making it out the other side to make comments!


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## jones57742 (Sep 8, 2007)

Sam: Believe me in that I am not making fun but just an outside observer and could not help myself.



Manthalynn said:


> But each hemisphere experiences over 12 hours of light at some point in the year. And some plants are day-length sensitive. (Delphinium/Larkspur are long day - they flower when they receive 16+ hours of light per day; Mums are short day...not sure what the critical photo period is for them...)


ah ha! ah ha!!

But I do not believe that I have a single plant in my tank which is not perennial!




Manthalynn said:


> Then again, this is a TROPICAL tank, and most tropical plants are day-length neutral ...


ah ha! ah ha!! again

But what I do not have a handle on is how refractive light near sunrise and sunset at the equator relate to what we do in our tanks but I believe (although could really be wrong here due to a physical concept) that is why 7100K bulbs assist in plant health and growth (although many folks think that I am insane for making this assertion).

TR


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## Manthalynn (Aug 23, 2008)

jones57742 said:


> Sam: Believe me in that I am not making fun but just an outside observer and could not help myself.


Don't worry, I'm not easily offended! 




> But I do not believe that I have a single plant in my tank which is not perennial!


Delphinium and Mums are also perennials, so being perennial doesn't affect day length sensitivity. Onions are long-day plants and I have one of those in my tank. But I'm not expecting it to flower and set seed...



> But what I do not have a handle on is how refractive light near sunrise and sunset at the equator relate to what we do in our tanks but I believe (although could really be wrong here due to a physical concept) that is why 7100K bulbs assist in plant health and growth (although many folks think that I am insane for making this assertion).


That is an interesting thought. The sun is daily traveling through different thicknesses of the atmosphere, so we receive different quantities of light (ooo! A changing rate problem! Quick, bust out the calculus!) At the end of the day, how much light do we actually receive, and of what quality (ie: wavelength) 

Can that amount be compressed into a shorter amount of time at a higher rate? At least, I think that was the point you were making. If it was, good point! I didn't think about that! If not, well, thanks for leading me to that thought anyway.

(Incidentally, and totally unrelated, tomatoes are day-length neutral but perennials...we just can't overwinter them outside of the tropical regions so we treat them like annuals)


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## jones57742 (Sep 8, 2007)

Manthalynn said:


> Delphinium and Mums are also perennials, so being perennial doesn't affect day length sensitivity. Onions are long-day plants and I have one of those in my tank. But I'm not expecting it to flower and set seed...


Thanks Sam: I was not aware of this.




Manthalynn said:


> That is an interesting thought. The sun is daily traveling through different thicknesses of the atmosphere, so we receive different quantities of light (ooo! A changing rate problem! Quick, bust out the calculus!) At the end of the day, how much light do we actually receive, and of what quality (ie: wavelength)
> 
> Can that amount be compressed into a shorter amount of time at a higher rate? At least, I think that was the point you were making. If it was, good point! I didn't think about that! If not, well, thanks for leading me to that thought anyway.


No. It is sorta your first paragraph but rephrased
"the time variance of the K value of the energy* and its' intensity"

Envision a 24 hour graph with the X axis as time, the left y axis as K value and the right y axis as intensity*".

This is a hypothetical since, as I said, I do not have a good handle on it:

[1] one hour before sunrise the K value is 1000 and the intensity becomes a positive value A

[2] one hour after sunrise the K value is 6000 and the intensity is 4XA

[3] etc. and obviously the Y plots would not be anywhere close to linear and would have to be averaged over a year or more in order to appropriately represent atypical atmospheric conditions.

*I say energy and intensity as plants perceive energy which our eyes do not (lol but an example is that our skin does: ie. sunburn) and intensity as lumen is an inappropriate measurement for plants.




Manthalynn said:


> Incidentally, and totally unrelated, tomatoes are day-length neutral but perennials...we just can't overwinter them outside of the tropical regions so we treat them like annuals


Two items:

Have you ever noticed the difference in taste between hydroponically grown tomatoes in the winter versus in the summer? (I have very limited knowledge of this due to the proposed construction of farms in Far West Texas.)

Would pecan trees (which are indigenous to West Texas) grow on the Equator?

These are serious questions and I would appreciate you thinking here.

TR


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## Manthalynn (Aug 23, 2008)

> Have you ever noticed the difference in taste between hydroponically grown tomatoes in the winter versus in the summer?


I'm not good at qualifying tastes because I don't have a sense of smell, which seriously impedes my sense of taste. Really, I just prefer home grown and freshly picked tomatoes over any you get at the store, vine ripened or otherwise. I prefer home grown because you can pick them at a later stage of ripeness that would be damaging to the fruit if it had to ship at that stage and be bruised to death. (The joys of living in Coastal california, I have tomatoes almost 8 months out of the year...)


Most commercial tomatoes (hydoponic, hothouse, or field grown) are picked at physiological maturity, which means the tomato is green but has reached a level of maturity where it is able to ripen. It also usually has a star of pink or red on the bottom (10% of the tomato is pink...this is called "star breaker" stage) These are picked and sent to a distributing warehouse where they are gased with ethylene (a natural, plant-derived gas that promotes ripening and senesence) to turn them red so they can be sold. This ethylene process would occur in nature too, and is harmless, we just help it along in the stores by concentrating it. (This is why if you get a fruit that isn't quite ripe, just set it on your counter or in a paper bag and it will ripen on its own.) There is some debate as to whether vine-ripened (meaning red when they're picked) is more nutritious than green-picked, but no one knows for sure (including my professor who specializes in post-harvest procedures). The industries current scientific guess is that once it has reached physiological maturity, the fruit has all the nutrients it's gonna have so it doesn't matter if you pick it already, even though it doesn't look as pretty.

The other major reason we don't treat tomatoes as perennials in the non-tropics is because they are so susceptible to diseases outside of their native territory. I suspect that is the biggest reason we replant every year. I noticed my tomato plant in my backyard is coming back (I never bothered to rip it out so it's sending out green stems again) but it won't ever produce very well because it's probably picked up so many diseases and viruses. 



> Would pecan trees (which are indigenous to West Texas) grow on the Equator?


Thanks for the opportunity to research this! The question is not whether they will grow, but will they produce fruit (ie: the nut, which is not a true nut, but a drupe, like a peach or almond). 

First, let's stick with the Delphinium that I am familiar with to explain why my qualifier to your question is necessary. If a delphinium plant never achieves 16 hours of daylight in a day (ok, it's really the length of the darkness - to satisfy my botany prof - but let's stick with calling it day length) it will never flower. It will just keep growing vegetatively (ie: the green parts like stems, leaves, and roots) but never set flower. And in this plant and fruit trees, we want them to set flower. Otherwise they're no use to us.

Now on to the pecan tree...

According to the Texas Pecan Growers Association "The United States produces at least 80 percent of the world's pecans. The U.S. crop typically ranges between 300 and 400 million pounds. Other countries that produce pecans are Mexico, Australia, South Africa, Israel, China and Argentina."

None of these locations are near the equator so they do receive some variation in day length. Pecans prefer a season of more than 200 frost-free days and a hot growing season is necessary to mature the nut. So far I can't find anything about them being day-length sensitive, however. 

They may be predominantly grown in the US simply because other countries have their own native, comparable nut trees (such as the case in Mexico...why go to the trouble of importing a crop that most likely will not do as well in your area as native counterparts...introduced _crop _species usually have to deal with heavier pest pressure than native crops...weeds are a completely different story - introduced, non-natives tends to do better in these cases...)

I'll ask my Professor today because she specializes in fruit science and has a whole drawer full of info on pecans. Plus she's a wealth of information on physiology, which we're wondering about here. She'd be more than happy to spend a few minutes explaining this to me.

Hope that answered some of your questions, anyway! Hey, I did learn that pecans require lots of water, so perhaps you can create some sort of bonsai pecan pauladarium? Just kidding...


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## jones57742 (Sep 8, 2007)

Sam:

Thanks a bunch for spending so much time on your reply.

Where I was coming from on the tomatoes is that a problem in hydorponic gardening is that they "just don't taste as good" in the late fall and winter months:

Obviously genetic engineering is going on here and

also importation from "down under" does not seem to help.


ah ha! ah ha! on the pecan trees they are not perennial and without the annual cycles not only will they not bear fruit they will not survive. 

TR


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## Manthalynn (Aug 23, 2008)

Yes! I am back among the living now that finals are over. 

Ron, no, Pecans are NOT annuals. They are perennials. (Any plant that lives more than one season/year are perennials. A big clue is that they have woody parts. That's what I typically look at to decide if I'm not sure.) It's only taken me years of botany classes to remember the difference between Annual, perennial, and biennial (only lives for two years...lettuce is a bi-ennial), so don't feel bad.

You are correct, however, that they need seasonal changes to produce nuts. Here's the research I uncovered. All of the following info comes from various volumes of "Pacific Nut Producer".

Pecans have "on" and "off" years, which means that one year they produce a HEAVY crop and the next year, they produce a much smaller crop. And then another heavy one, etc. Most avocados are like this, too. From what I read, "on" years do not appear to be related to the year the tree was planted as it discussed all of a region experiencing an "on" year. I'm assuming that means that they get into a cycle that relates to the climate some how. (Probably kind of like natural El nino and La nina cycles here on the west coast) Not exactly related to our discussion, but interesting all the same. 

Direct quote: "Most pecan varieties require between 400 and 700 hours of temperatures in the 32 - 45 degrees F range during dormancy to break bud, bloom, and set fruit normally in the spring....Once there has been adequate chilling, a stretch of warm weather will trigger breaking of dormancy."

So from this, we know that each year, the tree must receive a certain amount of hours of cold for it to start its cycle properly. Let's say January 1st has 4 hours that day/night that were below 45 degrees F. The next day, there are no hours that fall below 45 degrees, then the next there are 3 hours of cold, then 5 hours of cold the next day. In these 4 days, the trees have accumulated 12 hours of cold. Does this explain what it means for pecans to need 400+ hours of cold to produce properly? This concept has become so old hat to me I can't remember if it's a "well duh!" concept or slightly more difficult to grasp. I seem to remember my classmates having difficulty with it. 

"Shortening day length and perhaps cooler temperatures signal to your pecan trees that it's time to make preparations for winter dormancy - preparations which include storage of adequate carbohydrate and nitrogen to meet tree requirements through winter and into the first part of spring."

Ok, so we know that they need a certain amount of hours of heat to fill the nut. We know that they need a certain amount of hours of cold (culturally speaking since in physics there is no such thing as "cold", just the lack of heat) to flower properly. And we know that the change in day length signals the tree to carry out certain metabolic activities.

I learned from my prof that if it were a case of just needing colder temperatures, you can achieve this on the equator by just going up in elevation to a location that does get cold. But I'm going to assume from my research that pecan trees do indeed need varying day lengths.

There, we finally have an answer. Maybe not THE answer, but an answer all the same. Wow, I sure learned a lot! Thanks for asking me so I could learn about this!


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