View Full Version : i just dont get my ph

12/15/2007, 05:58 PM
hello guys, almost 9 months into hobby and i dont understand why im getting 8.3 on my ph test kits (aquarium pharma and salifert) and 8.04 on my reefkeeper 2 ph meter, it doesnt matter how manny times i recalibrate it, it just doesnt match my test kits, eventually i wanted to use the reefkeeper for controlling a calcium reactor with co2, but taking on account the amount of difference between ph results, i could overshoot my ph and cause more harm, is anybody experiencing the same dilema, any ideas??

At night my ph drops to 7.8 and during the day it could go up to 8.2 at least thats what my reefkeeper tells me, btw i do have a little problem with excces co2, because if i close all windows my ph will drop to as low as 7.58 per reefkeeper, i tought that at this ph level everything would die no????, another thing is that my alk is at 6dkh, and i cant dose 2 part because i already have a high ph per my test kits.

so please enlighten me,
how can i raise alk without affecting ph?
why am i getting different readings on test kits and ph meters??
will a calcium reactor raise alk,cal,ph???
should i test for magnesium????

i have been at the chemestry forum, but chemestry is not kind to me, its hard for me to understand, is there anyone out there that could explain it to me easily, (like get a cal reactor, get a co2 bottle, the bubble counter does this, conect the ph probe here, first dose this amount, use this media) something easy.



12/15/2007, 06:10 PM
I would trust the reefkeeper before the test kits anyday.


12/15/2007, 10:06 PM
With what solutions was the ReefKeeper calibrated? I doubt that it's accurate.

A limewater reactor will help raise pH. The CO<sub>2</sub> reactors will tend to reduce pH.

12/15/2007, 10:21 PM
<a href=showthread.php?s=&postid=11392422#post11392422 target=_blank>Originally posted</a> by sanababit

and i cant dose 2 part because i already have a high ph per my test kits.

so please enlighten me,
how can i raise alk without affecting ph?

Please check first but I think if you use un-baked baking soda then it will increase your ALK and lower your PH just a tad.

If you use Baked baking soda then it will raise both.

But please don't take my word on it. I just thought I read it somewhere.

12/15/2007, 10:26 PM
Do you check only in the morning?

12/15/2007, 10:31 PM
Also I don't put much trust in test kits. If you are sure that you calibrated your RK probe right then I would trust that over a test kit. How old is your prob? You may also want to goto RK's forums page and ask if you are doing it right.

After that I'd trust the RK over any test kit.

Here's a pic of a PH on my tank on the same aquarium water with 2 different batches of salifert test kits.


12/15/2007, 11:38 PM
the time of day you test for the pH will matter also. make sure when using the test kits, test at the same time everytime.

But as others said i would trust a pH probe over a test kit.

12/15/2007, 11:54 PM
Upon reading more closely, I'd dose the alkalinity up to at least 7 dKH with some baking soda dissolved in water. That shouldn't hurt anything, whichever pH results are correct.

12/16/2007, 02:01 AM
thanks for all the help guys, to make things a little clearer, it doesnt matter at what time i test ph, if i do it in the morning using test kits i still get a different reading between my reefkeeper and kits, its always like a .20 to.25 difference, the solutions i use to calibrate my probe are 7ph and 10ph and the probe is only like 5 months old.

so using baking soda would raise my alk without raising ph????
how much baking soda should i use for a 80 gal tank with 30 gal sump, 110 gal total??
should i check for magnesium???
my cal is at 400 ppm, amm 0, nitrite 0, nitrate 0, temp 76, ph8.03, alk 6, phosphate 0, im running carbon, phosban, sulphur denitrifier, cheato, im dripping calcium at about a drop every 10 seconds, i dose iodine once a week, alk buffer every 2nd day until i tested with kits and saw that i had high ph, cal buffer every 5 days since the corals i have dont use that much calcium, salinity 1.025.


12/16/2007, 02:11 AM
This calculator will help with a dose:


The added baking soda will lower pH a bit when added, and then raise it a bit after some aeration, but the change is small enough to be safe.

Testing magnesium is a good idea, but it doesn't affect pH. :)

Sometimes, probes are subject to electrical interference problems, either via the saltwater or the power lines. It's hard to say whether the kits or the probe are more accurate. I've seen that go either way.

12/16/2007, 05:04 AM
I agree with Bertoni about increasing alkalinity. What have you used to clean your PH probe? How did you clean it?

12/16/2007, 10:49 AM
i cleaned my probe once because it had two sponge like things on the bubble tip of probe, i used tap water and toothpick to remove them, this problem has been with me since i got the reefkeeper, i just dont understand what is causing this difference of ph readings, i want to trust my reefkeeper but my test kits tell me otherwise.


12/16/2007, 05:04 PM
If dosing some baking soda doesn't keep pH at at least 7.8 according to the pH meter, I'd work on the problem. Otherwise, I think I'd just enjoy the tank.