PH levels

[zerreissen]

Good afternoon all,

I've never had a really good handle on my PH levels. I've used the Salifert color test kits in the past, but I find them so hard to read that I don't feel comfortable relying on them. I recently purchased a Neptune Apex with a lab grade PH probe. I calibrated it using the 7 and 10 fluids. After calibration, my PH reading was around 7.0- 7.2 on the probe, which is pretty low for a reef system. I understand that consistency is usually more important than value, but I've read that low PH values can lead to slow growth for SPS and this is something that I've experienced in my tank. I'm using Kent superbuffer to increase PH and now it's around 7.6, but it's taking a while (I understand that it should be done over a period of time) and it's also raising my alk above ideal levels.

My questions are:

Should I be trusting the PH probe to get an accurate reading? If not, should I use a particular test kit?
If I can trust the probe, is there anything I can do to raise the PH that won't raise the alk?

Thanks!

[350gt]

Was wondering the same......although my range is around 7.92-7.98 on my RK unit.

[mkengr45]

I am in the same boat as you guys. I am using the Reefkeeper Elite and my ph varies between 7.7 and 8.0.......should we be trusting of the probe? I kept the calibration fluid in two plastic containers and have had them iun a cabinet, do you think they are still good for checking the probe? I wonder if its calibration has drifted. Do you think the calibration fluid is still valid?

[mkengr45]

I have to calibrate all kinds of stuff at my job (pressures, rpm, current, accelerometers, torque, temp, flow etc....) and I know that certain types of sensors can have an offset or drift over time. I also wonder if only using two test points for calibration is giving us the best accuracy. Has anybody looked into doing a multiple point calibration on one of these things, maybe the output of the sensor is non-linear?

[Big_Pun]

so chris are you dosing two part, how frequent are your water changes.

[zerreissen]

so chris are you dosing two part, how frequent are your water changes.

I'm currently manually dosing 2 part each morning with B Ionic (will soon be switching over to BRS dosing pumps). I generally do weekly water changes on the weekend, but have not in several weeks due to the holidays. I just calibrated my PH probe within the last week, my primary concern is, is it accurate enough to rely on for making PH value changes?

[Big_Pun]

I have a RKE and my ph swings almost a whole 1 point to 7.8-7.7 at night so that's when i dose my two part(BRS). I did have a prob at one point but I took my time on calibration and left it in solution 10-15 min to let it settle I even put my temp probe in solution to go with correct ph according to temp

[BSJF]

I doubt it is 7.2 or 7.6. You have to be real careful not to contaminate the calibration fluid (rinse with RO and dry between each). Also, leave it in the fluid a long time when you are calibrating it. You can backcheck it after you calibrate it. It should read close to 7 and 10 in each of the fluids. If it is off by more than 0.1, repeat the calibration process. Also, make sure the calibration fluids match the temp of the tank water. Calibrate each month.

[zerreissen]

Thanks guys,

My process for calibration: stuck the calibration packets on an algae clip in the tank for 20 minutes to adjust temperature. Took the #7 packet out, opened, dumped contents into a small glass jar, stuck probe in and left for 10 minutes. Once # 7 was completed, I rinsed the probe in tap water, took out the #10 packet, opened, dumped contents into a SECOND glass jar stuck probe in and left for 10 minutes.

I ordered more calibration packets (only had one set) and will back check and re calibrate if needed. I'm assuming it's ok to dump the fluid into a glass jar to hold the PH probe? I'll also make sure to use RO/DI water to rinse the probe and dry it in between (which I didn't do, just shook it off) and perhaps stick the Temp probe in with the PH probe (I have temp compensation enabled).

[Meslo]

just stick the probe in the packet the fluid comes in. then you dont have to worry if there was soap or whatever still in the glass.

[Squiers007]

I work in a water quality lab and when we calibrate our pH probes (which we do everyday I might add...) we only use 3 calibration points 4,7, and 10. Since we are only reading pH levels between 7 and 8.5ish for our tanks, using only 2 calibration points is fine. As others have said, make sure to leave the probe in the calibration fluid until the value stabilizes. One way to make this go a bit faster is to swirl the probe in the fluid so it is evenly mixed. We use stir bars and have the liquid constantly stirring while calibrating and taking readings. I'm not sure what kind of drift the probes have but if possible I would recalibrate every month (the more often the better).

[zerreissen]

Thanks guys, I calibrated the probe right before I put it in the sump a couple of weeks ago. I just bought 12 #7 and #10 packets so that I can calibrate on the first weekend of every month. I re calibrated by putting the probe directly into the packet and had the packet held with an algae clip in the water in the sump (for temp sake) and left it there for 25 mins. PH now reads 8.09, which is much better.