help me lower my PH please!

[cinnamongirl]

Hello

My PH has been at 8.3/8.4 (which was high to begin with) since I started cycling 3 weeks ago, but the last few days, it has gone up even more. The last two days it was 8.5, this morning it was 8.6!! What's going on? I'm using a hand-held PH meter and double checked it today with a Red Sea color test. I also have been double checking the calibration on my meter weekly.

There's nothing in my 75g tank but 100lb LR and 4"DSB.

I've been doing weekly 30% water changes the last three weeks while it's cycling, plus topping off daily with a gallon or so of either RO/DI or SW, depending on my salinity level that day.

Salinity is at 1.023 right now (slowly raising it back up to 1.025)
Ammonia and nitrite=0, Nitrate=10. I'm not running any lights at all right now, just my powerheads and protein skimmer.

I ordered a det.kit and cleanup crew to be delivered Wednesday next week (5 days from now) because I thought I was on the right track, but now this! I want this cleared up before they get here!

HELP

[Randy Holmes-Farley]

You are adding no alkalinity supplements or buffers?

Are you using artificial live rock?

Do you know the alkalinity? Is it unusually high?

If the answers are basically no, then the high pH is likely a measurement error. You might check the pH meter in borax to see that the calibration is correct:


http://web.archive.org/web/20021015005420/www.animalnetwork.com/fish2/aqfm/2000/feb/bio/default.asp

[cinnamongirl]

I added the 2-part calcium/alk supplement from CoralLIfe last week, but decided not to continue adding the prescribed amount until I better understood my readings. I haven't tested calc or alk this week. Calcuim was low at 320 the last time I tested it, and Alk was 3.9.

It's 50lb cured aquacultured figi from That Fish Place, 20 lbs figi premium from Dr. Mac and Sons online, and 30 lbs of base rock.

I calibrated the PH meter with two adjustment screws, one at 4.0 and one at 10.0 in PH calibration solution. I also ran a Red Sea test against a color chart, and it showed at the highest reading, too.

I'm at a loss!

[Randy Holmes-Farley]

Most meters cannot be calibrated at pH 4 and 10 (although some computer controlled types can). Usually it is 4 and 7 OR 7 and 10.

What brand and model is it?

[cinnamongirl]

I "think" it's Hanna Instruments.
It looks like this one:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=42291&item=4345074148&rd=1

[Randy Holmes-Farley]

I've not used that model, but I'd be a bit surprised if you can accurately calibrate it with pH 4 and 10 only.

Does it say that you can do that in the directions?

[cinnamongirl]

The directions say to calibrate it at 4 on one point, then any other solution for the other point. It says the most common is 7, but doesn't say it MUST be 7. Regardless, my chemical test is still saying 8.6.

Here's something interesting too... i just tested my RO/DI water I use for manual topoff at 8.9 PH and my SW for water changes at 8.7. Both have been aerated for over a week, kept at 80% in Rubbermaid.

I'm very lost :(

[Randy Holmes-Farley]

pH test kits are often off by quite a bit. That is why I'm discounting it a bit.

Also, it is certainly possible that you have high pH, but it is rare to have high pH all day long unless you are using high pH alkalinity additives, or are using artificial rock that is not fully cured.

RO/DI water is not accurately read by pH meters or kits as it has little buffering in it, and low ionic strength. Mine reads very high (and may be), but whether it is real or not, it won't change the tank pH appreciably (assuming the RO/DI is working). Folks like myself that use limewater add a solution with a pH of 12.5, and still can keep the pH down.


A couple of questions:

What time of day are you measuring pH? At the time just before the lights comed on what is the ph? Maybe the pH isn't really high on average, but just has a big swing. I can easily believe that, and the solution is different.

[indeep]

sorry wrong spot

[Randy Holmes-Farley]

I didn't want to give the link until we were sure that the pH was really 8.6, but if it is, this article describes a bit how to correct true high pH situations:

Solutions to pH Problems
http://www.advancedaquarist.com/issues/june2002/chem.htm

Here's something interesting too... i just tested my RO/DI water I use for manual topoff at 8.9 PH and my SW for water changes at 8.7. Both have been aerated for over a week, kept at 80% in Rubbermaid.


The pH for fully aerated salt water should not be that high. That too suggests measurement error to me.

[cinnamongirl]

Ok, I think I'm convinced that I need a better PH meter before I start worrying too much!

I typically run all my maintenance when I get home from work, around 6pm. Since it's been high, I started checking it in the morning 8am also, and there doesn't seem to be a difference between the two times. I'm not running lights at all.

[Randy Holmes-Farley]

OK, yes, I'd confirm the pH reading before acting on it. Perhaps check it in the borax. :)

[cinnamongirl]

I got some borax and check my PH meter in that. It read 9.8! So I recalibrated it using the 4.0 calib solution on one point, and the borax at 9.2 on the higher point. (was that what I should have done?) Now my tank is reading 7.7 which I can't believe, because my color tests are both reading 8.2-8.4. I think my PH monitor is CRAP!!

Can anyone suggest a good PH meter, so I don't make the same mistake twice!!!

[Randy Holmes-Farley]

No, you must use pH 7 and one other point on all except very sophisticated pH meters. Try pH 7 and the 9.2, if you can.

[hillrc91]

cinnamongirl,

I've had a Hanna instruments PHEP 5 for over a year now, and it's been very reliable and trouble free. The PHEP 5 is a simliar PH meter to the one in your link. To get an accurate reading, there are two key factors that you must adhere to:

1. As Randy indicated, a two point calibration is necessary. For calibrating the PHEP 5, I use PH 7.01, and PH 10.01 one time use packets every week. Since your dealing with saltwater, you'll get a more accurate reading if you calibrate using 7 and 10. The packets are available for $1.09 each from Drsfostersmith.com. (the PHEP 5 meter is also available there)

2. According to Hanna's directions, The electrode must be stored wet, perferably in a storage solution, and never in tap or distilled water. The electrode must also be periodically cleaned with a brush. Speaking from experience, I've left an electrode in a dry state, then tested my water and gotten a severely high reading. If all else fails, try buying a different electrode first.

Richard

[shan820]

4 to 10 is definately too wide of a pH range. Typically you dont want to span more than 4 units, and the closer your calibration points are to your sample readings the better. As previously suggested, 7 to 10 would be best. After calibrating, read the 7 again to make sure the calibration worked.