How to get an accurate pH reading with chloramine

[Trophy Husband]

First post..."hi"

When I test my water (both tap and tank) I get a pH reading of 7.6 using an API test kit both before, and after, adding Prime.

However, I've read here and elsewhere that chloramine skews pH tests and I know the tap water contains chloramine.

In addition, I'm doing CO2 for my plants and have a large piece of driftwood in the tank. I would expect a pH difference between tap and tank with the CO2 and tannins in it.

I'm wondering if;

a) I'm not putting in enough Prime (2 capfuls for 65gal at every WC)
b) the Prime doesn't impact the test and it's going to be skewed even after the chloramine has been "removed"
c) I'm using a bad test kit and I should get something other than API
d) I'm missing something else entirely

Thoughts??

[alron2]

I would take some aquarium water to the local pet store and have them test it or take it to someone who sales well supplies such as water softens or iron filters. What do you think? Welcome to the forum, looks like everyone has gone to the beach.
Ron

[DJW]

That chloramine skews the pH test is not something I have heard or seen before. Do you have a reference for this?

For the CO2, here is a test you can do. Put 1/2 cup of your pH 7.6 tank water in a cup and blow bubbles into it with a straw for about 30 seconds. This will dissolve enough CO2 to put the pH well below 7. Then test the pH with the low range pH test, the one that goes from yellow to blue (6.0-7.6). If the pH is under 7 it looks like there is a problem with the CO2 injection in the tank. If you still get 7.6 you can blame the test kit.

[Trophy Husband]

That chloramine skews the pH test is not something I have heard or seen before. Do you have a reference for this?

My mistake. it wasn't a false reading with the API pH test kit, it was a false reading with the API Ammonia test kit. Here's the quote and the link.

"a standard API salicylate-based ammonia kit ..... cannot distinguish between the free and bound ammonia so you continue to get a reading for ammonia." (because of the chloramine)

http://www.seachem.com/support/forums/forum/general-discussion/1368-prime-chloramine



For the CO2, here is a test you can do. Put 1/2 cup of your pH 7.6 tank water in a cup and blow bubbles into it with a straw for about 30 seconds. This will dissolve enough CO2 to put the pH well below 7. Then test the pH with the low range pH test, the one that goes from yellow to blue (6.0-7.6). If the pH is under 7 it looks like there is a problem with the CO2 injection in the tank. If you still get 7.6 you can blame the test kit.

What a great technique. ;) Sure enough, I did exactly what you suggested (blew for 1 min instead of 30 sec) and pH dropped to 6.8. Makes we wonder what's going on with my CO2 injection???!!

Big picture, it's not that big a deal. My pH in the tank is rock solid at 7.6 or thereabouts. And, rather than chasing pH, I'll just accept that the API test kit works and my pH really is 7.6.