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What would cause PH to go up in fish tank?


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#1 Guest_az9_*

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Posted 28 October 2010 - 05:01 PM

I thought I had the nitrification cycle all figured out until I recently purchased a PH meter. Seems the fish tank water is 8.1 in PH while the make up water from the well is 7.5. Is this normal? I was always under the impression that the nitrification cycle causes the PH to drop not rise?

Thoughts?

#2 Guest_donkeyman876_*

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Posted 28 October 2010 - 05:19 PM

Certain minerals like limestone can increase pH.

#3 Guest_smilingfrog_*

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Posted 28 October 2010 - 05:20 PM

Thoughts?


Just a couple off the top of my head. If the make up water is just replacing (or mostly just replacing) evaporated water, then minerals such as carbonates could be building up which will raise the pH. Also, if you've got any mortar or concrete in there, that could raise it as well.

#4 Guest_EricaWieser_*

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Posted 28 October 2010 - 05:37 PM

Please let me explain pH to you. There are two different definitions for it.

One was coined by a man named Arrhenius. He said that all acids release H+ into solution and all bases release OH-. So pure water with a pH of 7 would be when every single water molecule is in the form of H2O with no charge on it. And an acid would be a substance that releases H+ (also known as protons) into the water, causing some of the H2O to become H3O+. And a base is a substance that releases OH-. The range of an acid is from 1 to 6.9 and the range of a base is from 7.1 to 14. Exactly 7 is considered neutral.

When you apply Arrhenius's definition of pH to nitrogen compounds, it doesn't really explain why ammonia would affect pH because ammonia (NH3) doesn't donate an OH- to the water. Yet it is basic. That's where the Bronsted-Lowry definition of acids and bases and pH comes in.

Bronsted-Lowry (two people this time, working together) defined acids very similarly to the way Arrhenius did (they donate an H+) but the definition of a base changed to any substance that can accept an H+. This now explains why ammonia is basic; when ammonia (NH3) dissolves in water, it accepts an H+ and becomes NH4+.

The ions dissolved in your water can affect your pH if they are accepting or releasing hydrogen ions (also known as protons). The major source for an increase in pH is the substrate, especially if your substrate is crushed coral or chalk or limestone, or some other calcium carbonate rich mineral. A good test for the basicity of a substrate is to pour an acid on it (for example lemon juice) before adding it to your tank. If it fizzes when you put lemon juice on it, it's going to make your tank more basic. The fizzing your see is the base in the rock reacting with the acid in the lemon juice.

The most common method of making your water more acidic is by adding tannins. Dead brown leaves work, as do dry wood and mulm from dead plants. They slowly decay, releasing tannings and lowering your pH into the acidic range.

If I were you, I'd buy some test kits and learn about your water. See what concentration your ammonia, nitrite, and nitrate are at. You might even, if you're curious, test for dissolved calcium (GH) and dissolved carbonate (KH). It's fun to learn more about water chemistry when you keep fish. All of a sudden a whole bunch of things make sense. Many species of fish, for example, require certain water parameters and pH in order to be induced to breed.

I'll leave you with some helpful links.
Here's more information about the different definitions of pH: http://www.visionlea...ewer.php?mid=58
And here's some good graphs about nitrogen converting bacteria and the nitrogen cycle: http://www.fishkeepi...ing-article.htm

#5 Guest_Skipjack_*

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Posted 28 October 2010 - 05:55 PM

99% chance that your make up water, while replacing evaporated water is concentrating buffers. Each time you add your well water, you are adding calcium, which never leaves the system through evaporation, only leaves with water changes. If your water changes don't exactly equal your make up water, your ph will rise. Slow drip some muriatic, or don't worry about it a bit, I am certain your Lepomis don't mind your 8.1 water at all. My local streams are 8.3.


Edit: think I just reiterated what smiling frog was saying.

Edited by Skipjack, 28 October 2010 - 05:56 PM.


#6 Guest_az9_*

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Posted 28 October 2010 - 08:09 PM

99% chance that your make up water, while replacing evaporated water is concentrating buffers. Each time you add your well water, you are adding calcium, which never leaves the system through evaporation, only leaves with water changes. If your water changes don't exactly equal your make up water, your ph will rise. Slow drip some muriatic, or don't worry about it a bit, I am certain your Lepomis don't mind your 8.1 water at all. My local streams are 8.3.


Edit: think I just reiterated what smiling frog was saying.



Thanks for your comments.

I do test ammonia, nitrite, and nitrates on a regular basis. I just wasn't able to to afford a PH meter up until now and invested my capital in other components as the fish were and are doing well. I just assumed the PH in the tank should be lower than the make up water due to the actions of the autotrophic bacteria and was surprised to see it actually the opposite.

The tank is a 300 gallon epoxy coated stock tank with no limestone, concrete, or anything similar to it. The idea that adding the make up water is continually adding carbonates which aren't evaporating off makes sense.

In the make up water which comes directly from the well the Total Alkalinity as CAC03 is 343 and Hardness as CACO3 is 362 mg/l. Calcium is 97.4 mg/l with bicarbonates at 418.8 mg/l.

Edited by az9, 28 October 2010 - 08:10 PM.


#7 Guest_EricaWieser_*

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Posted 28 October 2010 - 10:35 PM

The tank is a 300 gallon epoxy coated stock tank with no limestone, concrete, or anything similar to it.


What substrate do you have? Just out of curiosity?

#8 Guest_PhilipKukulski_*

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Posted 29 October 2010 - 04:22 AM

Buy swimming pool muriatic acid,
not cement cleaning muriatic acid.

#9 Guest_gerald_*

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Posted 29 October 2010 - 11:35 AM

Water fresh from your well may also have more dissolved CO2 than water in the tank, and thus lower pH. As the excess CO2 off-gasses into the air, pH will rise. It's similar to what happens daily in a pond, where plants/algae consume the CO2 faster than it can diffuse in at the water surface, causing pH to rise. Ca+Mg hardness has very little if any effect on pH. It's mainly the carbonate and bicarbonate (= Alkalinity or "carbonate hardness") that does the buffering.

#10 Guest_centrarchid_*

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Posted 29 October 2010 - 11:37 AM

I thought I had the nitrification cycle all figured out until I recently purchased a PH meter. Seems the fish tank water is 8.1 in PH while the make up water from the well is 7.5. Is this normal? I was always under the impression that the nitrification cycle causes the PH to drop not rise?

Thoughts?



Yes, nitrification operating alone should reduce pH.

Can you measure carbon dioxide? If so, what is it? How is the hydrogen sulfide levels in your incoming water? Aeration / degassing of both chemical species could cause pH to increase following introduction of makeup water. Do have some sort of degassing column in place stripping out dissolved gasses?

How many pounds of feed do you add to system per day? If low, then evaporative concentration of carbonates could be going on as mentioned. If high, then double check measures and / or meter.

Edited by centrarchid, 29 October 2010 - 11:39 AM.


#11 Guest_Skipjack_*

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Posted 29 October 2010 - 03:31 PM

If I recall correctly, AZ9 is using a packed column to degas his well water, but correct me if I am wrong. Hey AZ9, why don't you show some of those pictures of your system, and show the RBC as well. I think it would give everyone a better idea of what you are working with, and it is a pretty slick set up.

#12 Guest_EricaWieser_*

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Posted 30 October 2010 - 11:35 AM

I did a project for my Process Control class where I built a P.I.D. controller to control the concentration of dissolved carbon dioxide gas in a fish tank with a CO2 diffuser. The goal was for the controller to turn on an air pump when CO2 was above 30 ppm, increasing release of the gas through the surface of the water and decreasing dissolved CO2 concentration back to levels healthy for the fish. In order to build the controller, I had to define a relationship between CO2 concentration in ppm and pH. I used the Red Sea CO2 test. Image of test kit: http://lh4.googleuse...mI4vSwIOrY_wPf6

I got this graph:

Attached File  CO2 concentration versus pH.jpg   26.25KB   2 downloads

Just in case you're curious about CO2's affect on pH.

Edited by EricaWieser, 30 October 2010 - 11:38 AM.


#13 Guest_az9_*

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Posted 30 October 2010 - 09:14 PM

Water fresh from your well may also have more dissolved CO2 than water in the tank, and thus lower pH. As the excess CO2 off-gasses into the air, pH will rise. It's similar to what happens daily in a pond, where plants/algae consume the CO2 faster than it can diffuse in at the water surface, causing pH to rise. Ca+Mg hardness has very little if any effect on pH. It's mainly the carbonate and bicarbonate (= Alkalinity or "carbonate hardness") that does the buffering.


Gerald according to a PHD down the road. Dr. Gary Miller, that has similar water chemistry to myself, I think you hit the nail on the head. Here's an email he sent me. I hope to try this soon.

Cecil;

Collect some well water directly into a jar -- not full -- , cap it and
agitate
like crazy. Now collect another sample of well water and compare the pH
levels.
My guess is that the well water (after aeration) has a pH closer to 8.7
because
of the high alkalinity we have around here. If your sample isn't that high;
areate it further.

Gary

#14 Guest_az9_*

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Posted 30 October 2010 - 09:21 PM

What substrate do you have? Just out of curiosity?


Erica,

No substrate actually. It's actually not an aquarium but a metal epoxy coated stock tank about five feet in diameter with a 55 gallon drum clarifer, and a rotating RBC all self built as per Steve VanGorder's Small Scale Aquaculture book.

You see I'm doing this all bassackwards. I'm building large RAS grow out systems before I install my first aquarium. I've got a in wall location all set for an large aquarium for native fish but haven't got to that yet. :roll:

#15 Guest_az9_*

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Posted 30 October 2010 - 09:32 PM

Buy swimming pool muriatic acid,
not cement cleaning muriatic acid.


Not sure I even need to reduce the PH but that's a good tip if need to do so. Thanks!

#16 Guest_az9_*

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Posted 30 October 2010 - 09:55 PM

Yes, nitrification operating alone should reduce pH.

Can you measure carbon dioxide? If so, what is it?


Not in the water. I have a meter but it is only for the air as I wanted to monitor C02 levels in the house. Not sure if I posted it here, but I was waking up with headaches in the morning and was afraid I was pumping the house up with C02. Turns out the C02 levels were not that high. The air C02 meter wasn't cheap and probably not necessary but it gave me peace of mind.

How is the hydrogen sulfide levels in your incoming water?


Again no way to measure it but when I first open the line to the well -- to fill the make up tank --there is a rotten egg smell. It dissipates very rapidly though. So there's some there! Sulfate in the original well water test showed 13.9 mg/l.


Aeration / degassing of both chemical species could cause pH to increase following introduction of makeup water. Do have some sort of degassing column in place stripping out dissolved gasses?


Not technically but the make up water barrel is filled with a garden hose and nozzle at high pressure, which obviously does some degassing. It also gets siphoned to second barrel adjacent to this barrel and is pulled up through filter material to trap iron in the filter material. Then pumped back to the make up water barrel. There is some additional aeration when the water is pumped back to the make up water barrel. BTW water turns gin clear within 24 hrs. Sure beats the iron filter I was renting!

Water is again aerated when it's in the tank dropping on to the RBC baffles to turn the RBC. And of course I have an agitator running 24/7 in the culture tank.

How many pounds of feed do you add to system per day? If low, then evaporative concentration of carbonates could be going on as mentioned. If high, then double check measures and / or meter.


Quite low. Probably a half a pound at most.

Edited by az9, 30 October 2010 - 10:14 PM.


#17 Guest_az9_*

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Posted 30 October 2010 - 10:04 PM

If I recall correctly, AZ9 is using a packed column to degas his well water, but correct me if I am wrong. Hey AZ9, why don't you show some of those pictures of your system, and show the RBC as well. I think it would give everyone a better idea of what you are working with, and it is a pretty slick set up.


No packed column presently. The one you probably saw on the Pond Boss site was used to degas and aerate well water for my trout pond.

Here's a link on this site to one of one of my RAS'. Soon both RBC's will be outside of the culture tank to keep particulate levels out of the RBC. I've made some other minor changes along with building my own chemical or resin free iron filter vs. renting one.

http://forum.nanfa.o...h__1#entry69005

Edited by az9, 30 October 2010 - 10:05 PM.


#18 Guest_az9_*

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Posted 30 October 2010 - 10:10 PM

I did a project for my Process Control class where I built a P.I.D. controller to control the concentration of dissolved carbon dioxide gas in a fish tank with a CO2 diffuser. The goal was for the controller to turn on an air pump when CO2 was above 30 ppm, increasing release of the gas through the surface of the water and decreasing dissolved CO2 concentration back to levels healthy for the fish. In order to build the controller, I had to define a relationship between CO2 concentration in ppm and pH. I used the Red Sea CO2 test. Image of test kit: http://lh4.googleuse...mI4vSwIOrY_wPf6

I got this graph:

Attached File  CO2 concentration versus pH.jpg   26.25KB   2 downloads

Just in case you're curious about CO2's affect on pH.



Makes a lot of sense Erica. This backs up what I'm hearing.

BTW your posts impress me so much I am picturing you as that new petit actress on NCIS Los Angelos that plays as a computer whiz!

#19 Guest_Skipjack_*

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Posted 30 October 2010 - 11:16 PM

Makes a lot of sense Erica. This backs up what I'm hearing.

BTW your posts impress me so much I am picturing you as that new petit actress on NCIS Los Angelos that plays as a computer whiz!

Thats great Cecil. She sure does her homework! :biggrin:

#20 Guest_EricaWieser_*

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Posted 31 October 2010 - 12:41 PM

*blushes* I'm just your run of the mill, normal overworked engineering major.




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