Ph testing question.. false positive? - The Planted Tank Forum
 
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old 01-25-2005, 11:46 PM Thread Starter
Planted Tank Enthusiast
 
Vinlo's Avatar
 
PTrader: (1/100%)
Join Date: Mar 2003
Location: Ontario, Canada
Posts: 719
Ph testing question.. false positive?

First some back story..

I recently decided to check my Ph after playing around with my reactor. Anyways, I tested my Ph (in order to get gauge on the CO2) and it was way high (7.6), I figured it was something to do with the reactor, so I checked my other tank.. also 7.6.

Hmm, I thought the Ph test was faulty, I bought a new one. Tested both tanks again, 7.6 again. I wondered what the water out of my tap would test at. I tested it (with both kits).. 6.6/6.4, way down from what it used to be a couple months ago.

Now the question(s)..

I assume that my Ph tests are giving me a false positive when testing the tank water due the a lower Ph in the tank than what the test reads? Is that how the Ph test usually work? If I start at 6.6 and add CO2 it will go down, no?

If this is not the case how could I possibly be getting a higher Ph reading that what is coming out of the tap? I am adding CO2 @ 50BPM into an inline reactor, with little to no surface agitation. I have not added anything to either tank that would effect water chemistry (I have not added anything to either tank period). Kh remains at 4-5. Plants pearl in the one tank, not in the other. Growth seems normal. Fish seem happy in both tanks. I really don't get it.

Any help for my troubled mind is greatly appreciated.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 2-T8 ODNO, AC300, HP CO2, Fluorite/Gravel

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 4-T8 ODNO, XP3, HP CO2, Fluorite
Vinlo is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 01-26-2005, 12:33 AM
Planted Tank Enthusiast
 
KevinC's Avatar
 
PTrader: (6/100%)
Join Date: May 2004
Location: Oshkosh, WI
Posts: 738
Quote:
Originally Posted by Vinlo
I have not added anything to either tank that would effect water chemistry (I have not added anything to either tank period). Kh remains at 4-5. Plants pearl in the one tank, not in the other. Growth seems normal. Fish seem happy in both tanks. I really don't get it.

Any help for my troubled mind is greatly appreciated.
1. pH test kits don't tend to go bad - the chemicals used are very stable and the solution is ethanol-based, so microorganism growth is unlikely.

2. Tap water pH readings must be taken after 24 hours - with a kH of 4-5, your pH should be >7. Let it rest, then test.

3. You are not adding anything to the tank except CO2?? That will be a problem real soon! Maybe the plants in the tank with no pearling are starved for nutrients!

4. Have you looked at a pH/kH/CO2 chart to determine what your target pH should be?

Kevin

Kevin

72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias

2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.
KevinC is offline  
post #3 of 9 (permalink) Old 01-26-2005, 01:40 AM
Doesn't like Kool-Aid
 
Momotaro's Avatar
 
PTrader: (52/100%)
Join Date: Feb 2003
Location: Hawthorne, New Jersey
Posts: 10,125
Quote:
You are not adding anything to the tank except CO2?? That will be a problem real soon! Maybe the plants in the tank with no pearling are starved for nutrients!
I am pretty sure he is fertilizing. I think he means he isn't adding anything to alter the water chemistry.

Did you try taking some water to the LFS and have them test the pH? I would give that a try, in addition to letting the tap water stand a day before testing that.

Mike

[SIGPIC][/SIGPIC]
Momotaro is offline  
 
post #4 of 9 (permalink) Old 01-26-2005, 02:17 AM Thread Starter
Planted Tank Enthusiast
 
Vinlo's Avatar
 
PTrader: (1/100%)
Join Date: Mar 2003
Location: Ontario, Canada
Posts: 719
Indeed, I meant adding stones or whatever that would change the water chemistry (kh, gh, ph, etc). I do fertilize - NO3, PO4, K, etc...

I will let some tap water sit for a day or so, see what happens.

Do you guys really think my tank water could be at 7.6? It has never been that high ever. It was always around 6.6-6.8 (what the charts say it sould be).

I have not taken the water to the LFS.. yet. Don't really trust any in this area.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 2-T8 ODNO, AC300, HP CO2, Fluorite/Gravel

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 4-T8 ODNO, XP3, HP CO2, Fluorite
Vinlo is offline  
post #5 of 9 (permalink) Old 01-26-2005, 09:40 PM
Doesn't like Kool-Aid
 
Momotaro's Avatar
 
PTrader: (52/100%)
Join Date: Feb 2003
Location: Hawthorne, New Jersey
Posts: 10,125
It is only a test.

I know some folks at the LFS can be pretty incompetent, but it is only a pH test...right?

Mike

[SIGPIC][/SIGPIC]
Momotaro is offline  
post #6 of 9 (permalink) Old 01-27-2005, 12:02 AM
Wannabe Guru
 
BlueRam's Avatar
 
PTrader: (0/0%)
Join Date: Sep 2004
Location: Seattle, WA
Posts: 1,666
Quote:
Originally Posted by Vinlo
Indeed, I meant adding stones or whatever that would change the water chemistry (kh, gh, ph, etc). I do fertilize - NO3, PO4, K, etc...
The pH/KH/CO2 table is assuming that you only have carbonate buffers in your system. If you are dosing phosphate you tank may by running off the phospate buffer which would result in a high pH. I have not done the math to prove this though. You can test by running CO2 into a jar of aged tap water with known KH/pH etc and seeing where the pH is at saturation.

Moved to Tucson.
BlueRam is offline  
post #7 of 9 (permalink) Old 01-27-2005, 02:26 AM Thread Starter
Planted Tank Enthusiast
 
Vinlo's Avatar
 
PTrader: (1/100%)
Join Date: Mar 2003
Location: Ontario, Canada
Posts: 719
BlueRam, are you saying that the addition of PO4 to the tank could be acting as a buffer?

I checked my aged tap water, pH 7.4-7.6


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 2-T8 ODNO, AC300, HP CO2, Fluorite/Gravel

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 4-T8 ODNO, XP3, HP CO2, Fluorite
Vinlo is offline  
post #8 of 9 (permalink) Old 01-27-2005, 02:43 AM
Wannabe Guru
 
PTrader: (8/100%)
Join Date: Dec 2003
Location: USA
Posts: 1,740
No, the phosphate levels we keep do not affect pH appreciably. You need high phosphate levels for it to start showing signs of being a buffer.

Well your kits look fine to me. The CO2 of your aged tap water is around 3-4ppm, which is right where it should be. The fact your pH kits responds to the lower pH from the tap is a good sign. And as Kevin already pointed out pH kits just don't go bad b/c they use very stable chemicals.

Seems to me something is wrong with your CO2 system or reactor. Leaks?
Rolo is offline  
post #9 of 9 (permalink) Old 01-27-2005, 11:01 PM Thread Starter
Planted Tank Enthusiast
 
Vinlo's Avatar
 
PTrader: (1/100%)
Join Date: Mar 2003
Location: Ontario, Canada
Posts: 719
No leaks, I am putting 50bpm into the reactors with no unddisolved co2 coming out. This is a strange one. I guess I will try an old internal reactor that I know works. If the pH drop using that.. then I know where the problem is I guess.

-edit-
Hmm.. I tested my water in my bubble counter. ph6.0. Crappy. That means something is messed up with my reactor. That's pretty crappy.

Now the thread changes. The only thing I have changed it I put in bioballs instead of plastic practice golf balls last weekend. Hmm.. maybe I put in too many? What makes no sense is that there is no undissolved CO2 coming out but there is Co2 in the reactor. Hmm.

Has anyone built an inline reactor that doesn't work? If so how did you get it work?


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 2-T8 ODNO, AC300, HP CO2, Fluorite/Gravel

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- 4-T8 ODNO, XP3, HP CO2, Fluorite

Last edited by Vinlo; 01-28-2005 at 01:58 AM.
Vinlo is offline  
Reply

Tags
None

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome