Bad PH probe??

[jeffroreefer]

I have recently set up a Kalkwasser drip system on my 38 gallon. My reason for doing so was to raise my calcium from the 350ppm that my tank has been stuck at regardless of my addition of liquid calcium. I also hoped that this would precipitate phosphates, raise and stabilize ph, and in turn help with other things. I have a pinpoint ph moniter that has been kind of flakey even though it's not even a year old (it bounces up and down in the hundredths place by about 3 up and down). I was maintaining a ph of about 8.2 using reef buffer about once every 4 days and it would drop to about 8.1 at night. I cleaned the end of the probe with a soft bristled brush and recalibrated the moniter because of the importance of ph when adding kalkwasser. Here's where it gets really confusing. After calibrating the moniter i discovered that my tank was really running at about 7.95 during the day. This was after administering kalkwasser for a full 24 hours. I added reef buffer to bring it up to about 8.2 while continuing the kalkwasser but to my huge dissapointment throughout the day it dropped back down, i added a little more buffer and by the end of the day it was back down to 7.95. My question to you is do I have a bad probe or do I have a bigger problem. I understood that Kalkwasser will raise the ph in any tank, why does mine keep dropping? My corals have never looked better and my fish are just fine, is this possible at a ph below 8? Please help me, i,m losing sleep over this.

 

[ALTI]

first you should double check the ph with a different probe or test kit. Check your alk too. if its low that could be the root of the problem.

is this tank in a basement or a room without alot of air circulation?excess CO2 can cause chronic low ph issues. ive always had trouble keeping the ph up in my basement tanks. after adding a larger skimmer and creating more surface aggitation in the tank the level raised up to acceptable levels.

 

[jeffroreefer]

Thanks Alti, I was really confused after i checked alk and it was around 5 meq/L. Checked my PH at my local store and it was around 8.4. Is my alk too high? or should i not worry about that? Also, my probe seems to be refecting the ph correctly just at a lower reading (it's stable at 7.98 during day and 7.90 at night) should i trust it and save the money on a new probe?

 

[ALTI]

buy a new probe or just a test kit. the alk is too high. thats why you have been struggling with the calcium level. do a couple water changes and it should go back to normal. kalc is not the best at raising the calcium. it work best to maintain the levels once you have them where u want them. a 2 part cal/alk additive is the way to go. use them till the levels are right and the kalk will keep it stable for a while.

 

[reverendmaynard]

When you calibrated, did it need much adjustment?

Did you use 7 and 4 or 7 and 10 reference solutions?

Did you adjust for temperature?

 

[kevin2000]

If you have had your Pinpoint a yr then odds are you need to replace the probe ... look closely at the probe and see if you still have fluid within the probe.

 

[jeffroreefer]

I used 7 and 4 calibration solutions.

 

[reverendmaynard]

<a href=showthread.php?s=&postid=6677982#post6677982 target=_blank>Originally posted</a> by jeffroreefer
I used 7 and 4 calibration solutions.

If you use 10 instead of 4, you'd be calibrating for the range you'll be using the probe to monitor.

Also, you didn't say if you corrected for temp. The reference solutions I have have a chart that show's it's PH at different temps. It's only exactly the PH it say's it is at like 78f. At 68f, which was my ambient temp when calibrating, the actual PH varied by as much as .15. I calibrated so the monitor read the PH that the chart showed for the temperature. I don't know for sure that that was the right thing to do, but why else would they show the PH values at different temps if you weren't supposed to take that into account?