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Discussion Starter · #1 · (Edited)
There has been some talk on here from time to time that has discussed plants and their effect on ph, saying that plants will increase ph to an 8+ level regardless of where it started. I had never seen it personally and despite reading a few books on keeping plants in a tank, none of those ever mentioned it either. The most technical book that I read was one written by Diana Walstad (Ecology of the Planted Aquarium) and despite looking back over it a time or two, there was never any mention of it. I figured if she didn't say it, with the tons of other technical jargon in the book, it just didn't happen, but I did want to prove it to myself.

Before this test, I had seen the ph value at the beginning of a lighting cycle be one value and then at the end of it be different, slightly higher, and believed to be the plants using the CO2 that is in the water. This slight change (never more than .1-.2) will usually reset itself after 4-6 hours as the surface movement of the water introduces O2 and more CO2 from the outside air. This happens on a continual basis and according to numerous sources, including Walstad, is the primary source of oxygenating your tank. But, since CO2 is in the air we breath and the creatures in the tank also create it, the CO2 levels in the tank sort of reset themselves after a few hours while the light is out and nothing is using up the CO2. Plants consume the CO2 when the light is on.

So, I decided to conduct a month long test on my shrimp tank since it is my only tank currently that is not injected with CO2. I like to keep the ph in the tank around 7.5 and to get it there I mix 80% RODI water and 20% tap. My RODI water usually starts out at 7.0, but after sitting out for about 12hrs it will read 6.8. My tap is 8.2. Anyway, doing the mixture gets me to a ph of 7.5-7.6. The tank is a 20G tall tank and filtered with an AC50. I did no water changes during the month and topped off every third day with an 80/20 mixture from a 2qt pitcher.

These were the results:

Day: 1/2/3/4/5/6/7

Week 1: 7.5/7.5/7.5/7.6/7.6/7.5/7.5
Week 2: 7.5/7.5/7.6/7.5/7.5/7.6/7.5
Week 3: 7.5/7.6/7.5/7.5/7.5/7.5/7.6
Week 4: 7.6/7.5/7.5/7.5/7.5/7.5/7.6

As you can see from this setup and my routine, ph is rock solid with some slight changes toward the end of the lighting cycle. About 90% of the test were taken in the evening between 8-10pm.

For the substrate I used safe-t-sorb which is a product used to absorb oil and made up of a few different types of fired clay chips ($5 for a 40lb bag at Tractor Supply). For plants I have 11 Crypts, 9 or so Dwarf Sagittaria Subulata, about 30 stems of a very fast growing stem that I don't even know the name of, some java moss, a mass of subwassertang that takes up about 1/5 of the tank and 2 clumps of Java Fern. So its a pretty good mixture of medium and fast growers with a Java Fern (slow). The light is a single bulb 24W T5HO that is on 10hrs a day.

I also tested gh and kh values once per week just to see. Both stayed in the 2-4d range. They always have.
 

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This sounds like a good test Ben. I'd guess that a raise in pH in a no water change tank would be the result of mineral buildup after evaporation/top offs, clearly it isn't from the plants. That would be 80% slower in a tank that has RO/DI water as 80% of its top offs. I wonder if we could fake this by boiling down a pot of water (or letting it sit a couple weeks to evaporate) and then testing for pH change vs a very dilluted pot (mainly RO/DI) with a lower KH)?
 

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What was the pH in your control with exactly the same environment but no plants and no light?
 

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....has no life....
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Discussion Starter · #4 ·
My water source was 7.5. I measure that before I add to the tank.

Not a scientific experiment where there are test and control pieces. This however, doesn't invalidate the testing.
 

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My water source was 7.5. I measure that before I add to the tank.
Fine.

Absolutely correct and I believe all your measurements.

My point has always been plants will increase pH due to lowering the carbon dioxide.

I observe that by conducting tests where the same conditions are in a control group that was also kept in darkness. The result was the tanks with plants all had pH rise so that the lowest pH planted was much higher then the highest non planted/lit tanks.

With substrates varying from crushed coral, oyster shells, play sand, bare bottom, peat moss in darkness and not planted had various pH values from 6.8-7.2 or so. In the test jars with the same substrates planted an lit all had the pH rise to 8.4-8.8 (purple on api high range test kit).

My old 55g mixed reef tank had pH rise from 7.6 to api test purple by adding baking soda. Then a few days later it was back down again. Adding several macro algaes the pH rose to 8.4+ and stayed there for years. Plus fish with the first signs of ich recovered and trippled in size over the next year. With kh low pH did drop at night to 7.9. With higher values of KH there was less pH drop. But either way the lowest pH with plant life (7.9) was much higher then highest non plant life ph (7.6).

All your test have shown is that your particular setup maintained the initial conditions of your water. Without the plants your pH may have dropped. You simply have not tested that condition.

my .02
 

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....has no life....
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Discussion Starter · #6 ·
Plus, why would I want to setup a tank with no plants and light? What is the point of that? What I care about is what I plan to have....not compared to something that I don't.

That is like saying that fish cause the presence of ammonia.....did you need a tank without fish to show the differences to prove it?

If you have someone who has done a scientific experiment on a tank and proved that the ph kept going up from it having plants in it, and also proved it wasn't some other issue in the tank that may have been causing it, by all means provide a link for everyone to read.

Your tanks don't prove that, by the way. You do zero water changes, no water movement, and have a substarte that could all be the cause of increasing ph values.
 

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....has no life....
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Discussion Starter · #7 · (Edited)
Fine.

Absolutely correct and I believe all your measurements.
With a little sarcasm

My point has always been plants will increase pH due to lowering the carbon dioxide.
I don't debate this point, but the fact that the carbonates never return to the water may be your issue. CO2 returns to the water by water surface movement, which your tanks are absent of. Could be the problem already why your tanks increase in ph. But...you do have other possibilities.

I observe that by conducting tests where the same conditions are in a control group that was also kept in darkness. The result was the tanks with plants all had pH rise so that the lowest pH planted was much higher then the highest non planted/lit tanks.
Your jar test lacked a lot of things that is probably the result of your high ph. It wasn't the plants that caused your high ph, but maybe a culmination of things like your substrate, NO water movement or flow, NO water changes. All the more reason to emphasize doing these things.

With substrates varying from crushed coral, oyster shells, play sand, bare bottom, peat moss in darkness and not planted had various pH values from 6.8-7.2 or so. In the test jars with the same substrates planted an lit all had the pH rise to 8.4-8.8 (purple on api high range test kit).
Like I said, if you have anyone that has proved it was the plants and ONLY the plants that caused the raise to occur, post a link. If this elimnates your substrate, you still have to prove it wasn't your lack of flow, or lack of water changes.

My old 55g mixed reef tank had pH rise from 7.6 to api test purple by adding baking soda. Then a few days later it was back down again. Adding several macro algaes the pH rose to 8.4+ and stayed there for years. Plus fish with the first signs of ich recovered and trippled in size over the next year. With kh low pH did drop at night to 7.9. With higher values of KH there was less pH drop. But either way the lowest pH with plant life (7.9) was much higher then highest non plant life ph (7.6).

All your test have shown is that your particular setup maintained the initial conditions of your water. Without the plants your pH may have dropped. You simply have not tested that condition.
Then it also proves that where your setups and my setups differ as my tank can be the "control test" to yours The difference lie the issue at hand and why you see increasing ph values that stick at 8.4-8.6 and never budge. NOT THE PLANTS CAUSING IT! With a kh of 10dkh or after I lower to 3-4dkh, I assure it is not lowering without plants being there.....I don't need a bunch of controlled test to tell me that and you shouldn't either. If you do, you should go back and do more reading.

It is not just initial conditions...it has maintained that value for 5+ months. However, I did not test everyday during that time. It is a value that has always been there even before plants.
 

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Discussion Starter · #8 ·
I also went to plantedtank.net and started a thread there. Gave the situation and what has been discussed here and asked what others see with their planted tanks. Of the 54,000+ members, not a single one reported seeing increases that weren't something that plants using up the CO2 and then resetting at after the lighting period.
 

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With a little sarcasm
absolutely no sacasm felt or intended. Simply accepting your results as stated.
I don't debate this point, but the fact that the carbonates never return to the water may be your issue.
Dr Randy holes-farly had an old article which reported with equations that the forward aerobic nitrogen cycle used up alk (KH) but that alk was returned in the same exact ratio as used up by both macro algae and bacterial action consuming the resulting nitrates. so carbonates are returned to the system by plants consuming nitrates.
CO2 returns to the water by water surface movement, which your tanks are absent of. Could be the problem already why your tanks increase in ph. But...you do have other possibilities.


Your jar test lacked a lot of things that is probably the result of your high ph. It wasn't the plants that caused your high ph, but maybe a culmination of things like your substrate, NO water movement or flow, NO water changes. All the more reason to emphasize doing these things.


Like I said, if you have anyone that has proved it was the plants and ONLY the plants that caused the raise to occur, post a link. If this elimnates your substrate, you still have to prove it wasn't your lack of flow, or lack of water changes.

My old 55g mixed reef tank had pH rise from 7.6 to api test purple by adding baking soda. Then a few days later it was back down again. Adding several macro algaes the pH rose to 8.4+ and stayed there for years. Plus fish with the first signs of ich recovered and trippled in size over the next year. With kh low pH did drop at night to 7.9. With higher values of KH there was less pH drop. But either way the lowest pH with plant life (7.9) was much higher then highest non plant life ph (7.6).


Then it also proves that where your setups and my setups differ - lie the issue at hand and why you see increasing ph values that stick at 8.4-8.6 and never budge. NOT THE PLANTS CAUSING IT! With a kh of 10dkh or after I lower to 3-4dkh, I assure it is not lowering without plants being there.....I don't need a bunch of controlled test to tell me that and you shouldn't either. If you do, you should go back and do more reading.

It is not just initial conditions...it has maintained that value for 5+ months. However, I did not test everyday during that time. It is a value that has always been there even before plants.
Again in my 55g the ph rose with no other changes.

again in my 1g neon nano with a soilmaster select and peat moss substrate the initial pH was 6.5 and rose to 7.2 a day later. Then to 8.4 over then next few weeks.

Again and most important when I did a test with a dozen quart jars, with the same water and the same substrates the one with lighted plants all had the pH rise to above 8. the ones with no light and no plants had various pH values ranging from under 7 to just above 7. If you do not accept those experimental results or are curious you could duplicate that for yourself.


my .02
 

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Discussion Starter · #10 ·
If I felt I could get a get a bunch of jars or containers and was able to provide them flow or filtration, I would gladly conduct my own test.

I will concede that having plants could cause issues in your tanks....and most of us would look at an increasing ph to the mid 8 range, no matter the starting value, as an issue. But I would say that it really isn't the plants that cause the issue in the same sentence. If you looked at both of our tanks, the common thing is the plants. If you see the ph increases you mention and I don't....it is not the common thing that is creating the issue. Where we differ - is. That is in water flow or filtration and water changes. Substrate may be different also, but as you've said you tested multiple substrates so we'll eliminate that item.

Your ph increase comes from a culmination of things, IMHO. Lack of flow, filtration, adequate fresh water, abnormally high TDS values, just to list a few. But one thing my tank proves and your tank to some extent, it is not the plants causing it.
 

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If I felt I could get a get a bunch of jars or containers and was able to provide them flow or filtration, I would gladly conduct my own test.

I will concede that having plants could cause issues in your tanks....and most of us would look at an increasing ph to the mid 8 range, no matter the starting value, as an issue. But I would say that it really isn't the plants that cause the issue in the same sentence. If you looked at both of our tanks, the common thing is the plants. If you see the ph increases you mention and I don't....it is not the common thing that is creating the issue. Where we differ - is. That is in water flow or filtration and water changes. Substrate may be different also, but as you've said you tested multiple substrates so we'll eliminate that item.

Your ph increase comes from a culmination of things, IMHO. Lack of flow, filtration, adequate fresh water, abnormally high TDS values, just to list a few. But one thing my tank proves and your tank to some extent, it is not the plants causing it.
My specific pH may be that value for whatever reasons.


My experiment with the jars prove that the plant actions and only the plant action resulted in a higher pH.

A dozen jars, air pump, some air stones, and tubing couldn't be all the expensive. Plus some oyster shells, potting soil, SMS, peat moss, sand as well. And a couple of styrofoam coolers and a light.


After a couple of weeks or months you could also throw in some feeder guppies also. But then you have to figure out what to do when the guppies live for over a year in the planted jars. *old dude

my .02
 

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Ben, I really have enjoyed reading your findings on this. Granted the results were a bit predictable you did it in a very calculated manner.

Bob,

you have to figure out what to do when the guppies live for over a year in the planted jars. *old dude
I understand you have your 'methods' that for whatever reason make sense to you, but to the rest of us that is like me telling you to go bungee jumping but don't bother with the bungee cord, you don't need it. Actually it would be a waste of time!
 

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Discussion Starter · #13 ·
What you're not seeing is that my plants in my environment prove that it is the environment that makes the plant action cause the issue. Put a powerhead on your tank and I bet your ph starts to dip to normal values.

Why is it that Walstad never mentions what you see? Like I said before, send me any link to any article that backs up your hypothesis.
 

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What you're not seeing is that my plants in my environment prove that it is the environment that makes the plant action cause the issue. Put a powerhead on your tank and I bet your ph starts to dip to normal values.
Well I did have powerheads in my 55g when pH was 7.6 which is extremely low for a mixed reef tank. I'll accept your assertion in my FW tank pH will go below my normal values with increased circulation. That is not my point. My point is the pH will rise when plants are added to the tank. The effect of changing circulation is another question.
Why is it that Walstad never mentions what you see? Like I said before, send me any link to any article that backs up your hypothesis.


I give up why? Perhaps she never did the experiment I did.

I've given you much more then my hypothesis. Direct experimental results in a controlled environment. In order to disprove those results please post your experimental results. I'm not being sacarstic. Not using personal attacks. Just being scientific. Which requires one to conduct experiements not mearly ask for links or question why others have posted the same results.

my .02
 

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Discussion Starter · #15 ·
What my test proves is that plants do not cause a rise in ph. However, this can occur in certain situations...for instance, how your tanks are setup with no water movement or large influx of freshwater weekly. They need help or in this case may cause it with little to no help.

Your experiment proved to yourself that in a situation where this is no water movement or large influx of fw, plants can cause your ph to reach mid 8s. IT DID NOT prove that all plants in all situations cause ph to go up like what you see. Your test only tested your methods. The assumption is that the affect you saw is the same using all methods - which it is NOT. That is the point. My test proves this.

Plants in what we will call a "normal setup", where there are filters, circulation, and water changes cause a daily fluctuation and barring any situation like a super low alkalinity, do not cause a long term steady climb in ph to a permanent state perched in the mid 8s or higher for that matter. This may occur in situations or setups as you have provided and tested. For a normal setup, this does not occur.

As I said, my plants are no different than yours. The photosynthesis the exact same way, and use the nutrients the same way. Your plant "action" is no different than what is in my tanks.
 

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Growing plants under light consume CO2 and produce O2 and an increased ph. Plants in the dark consume O2 and prdiuce CO2 and a decreased ph. Decomposing plants produce complex organic Acids that will also cause the ph to drop.
 

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Discussion Starter · #17 ·
Growing plants under light consume CO2 and produce O2 and an increased ph. Plants in the dark consume O2 and prdiuce CO2 and a decreased ph. Decomposing plants produce complex organic Acids that will also cause the ph to drop.
This is the day-to-day fluctuations mentioned above.
 

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Aquatic plants can raise OR lower the Ph of aquarium water…even in tanks with modern filtration/aeration equipment. When plants are introduced, the existing Kh affects subsequent Ph changes (if any), as does the existing CO2 level and resulting avenue of photosynthesis. Among other factors, the relationship between Ph, Kh, CO2, and plant life is dynamic and the addition or subtraction of any of the four can affect the remaining three.

Just because the addition of plant life raised the Ph of the water in Bob's freshly filled jars, doesn't mean plant life will always raise the Ph in any given aquarium. With that, just because the presence of plant life didn't result in a fluctuating Ph in your established tank jrman, doesn't mean new plants lack the ability to cause an upward swing of Ph in someone else's tank...especially initially. And I'm unclear jr...did your experiment begin with the addition of new plants in a never-planted tank? Or were you measuring the daily Ph of an established ecosystem with existing plant life?

It seems these 2 experiments, Bob vs jrman, are not comparable.

The prediction of whether or not plant life will raise the Ph of any given tank, in my experience, would be based on the water chemistry of that given tank. So unless that given tank had water chemistry that mirrored the water chemistry in Bob's jars or jr's tank, I wouldn't expect an outcome that mirrored Bob's jars or jr's tank.
 

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Discussion Starter · #20 ·
Nobody is debating whether or not plants raise or lower ph, I think everybody gets it that they can and do. What they don't do is cause a high ph, high like starting at a 7.0 level and eventually get to 8+ values....at least in a normal tank. The day-to-day fluctuation is normal. On these particular points, chemistry doesn't matter. If a tank, any tank, any chemistry, has the ph go high and stay there...something is going on in the tank. Whether it is the situation created in Bob's tanks from his methods or a non-existent kh, it is not considered normal.
 
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