Apex salinity/conductivity question.

[Adam]

I've been mixing water with a refractometer for a couple months now. I calibrate every other use. Mixing to 35ppt and QT to about 30. So far fish, shrimp and feather dusters have been fine.

Today I finally connected the conductivity probe and went through the calibration sequence meticulously twice. It's now reading 38.5 and when I checked it with the refractometer which shows just under 35.

I don't want make knee jerk changes but which one should I trust as accurate? I can live with the apex reading higher as long as its stable. It's just the ocd part of me wants them to match.

 

[bcavalli]

The Salinity probes are notoriously inaccurate. But, you can use it to chart changes. I believe you can adjust it down to what your refractometer reads.

 

[Adam]

Thanks for the info. Now I just need to figure out how to lower it. I'm temp compensating it but any changes I've made don't get me any closer.

 

[bcavalli]

Your welcome. It's been a while and I sold mine after having the same issues. I'll try and find a post in the Neptune forums for you.

 

[bcavalli]

Looks like I was mistaken. I searched the Neptune forums and other than temp compensation and ensuring proper calibration it pretty much is what it is. Here is a link to the forum that has some suggestions on proper calibration. Sorry.

 

[Adam]

Thanks again Brett!

I've been doing a bunch of reading. From what I found the probe reads more than just salt. The Mag in the IO salt I'm using is reading around 1485 with a Salifert test. When you add to that the +/- accuracy of each they're both within range.

I'll still mix with the refractometer and use the probe to monitor for consistency and irregularities.

 

[bcavalli]

Your welcome Adam. I'm glad you got it figured out. I've read they are useful for monitoring. I'll bet they figured out how to correct the issues with the new version of the Apex. I believe the Salinity probe is included now.

 

[axio]

Yeah I want to test out those new probes as soon as the new units get here tomorrow *grin*

 

[danh]

I need to work on my ph. I highly doubt fora cond is right

alt="" /></a>

 

[Adam]

Here's what mine looks like. I haven't added any thing yet. Very low bio-load now. I filled the system on 6/1.

alt="" />

The pukani rock I used was cured & cycled and there was 2 decent size pieces of Tampa Bay rock too, about 12-15 lbs. After filling there was virtually no cycle. As of the last tests my NH4=0, NO2=0 and NO3=4. I did a 50gal water change on Saturday but haven't tested again yet.

What is your Cal & Mag at?

 

[danh]

My alk is pretty high, just over 10 from trying to dial in my kalkwasser so I assume my cal is too. I haven't tested either of them. I'm using red sea salt and my coral bare right now. I don't really feel like I'm going to need to adjust much just yet.

 

[Adam]

I haven't dosed anything yet. I'm using IO salt and the Alk is 7.5 for me, Cal is 458 and Mag is 1485. I plan on bumping the Alk up this week. I used IO salt for startup do to cost. I've gone through just about 3 boxes since February and have one left. Once it's gone I'm switching to RC.

If you're dosing Kalk how come you're not testing Cal & Mag in addition to Alk? I would think you would want your baselines before dosing. My numbers above are from 6/13 and I plan on testing everything tonight then start working the Alk up over the next couple of days based on the test numbers. Granted I only have a leather and the fish in mine right now, so I wasn't too worried about the low Alk.

I'm really interested in what your Mag is at to compare my Cond reading to yours.

 

[danh]

I'll test them tomorrow. I haven't tested mag because I don't have a mag test kit

 

[Adam]

Hey Dan, Did you get a Mag kit? My Cond is consistently reading 3.3 to 4.5 higher than the refractometer, which is showing pretty much 35 every time I test. It would be good to correlate our numbers to see if there is anything to what I've been reading.

 

[morganatlanta]

In my experience, the Apex salinity probe is so wildly variable and inaccurate, I'm not sure having it even for monitoring is worthwhile. Occasionally it will settle in for a while at one reading, but then it will jump to another, and it isn't uncommon to see it jump +/- 3 ppt for a minute or so at various points during the day. I'll be interested to see if they have done anything with the new one.

Never, *ever* take any action based just on the reading from the probe. You absolutely need to validate any reading with a freshly calibrated refractometer.

 

[danh]

I ordered the mag kit. Waiting for it to come in. I'm reading 29.4 now. Since I set up the new Apex 5 days ago it's been on a fairly steady decrease 28.67 to 27.5. I guess I'm on the opposite end from you though. It does measure any ions through conductivity. Calibration does need to be done well and bubbles can affect it. I've tapped mine several times to make sure I had no bubbles in it.

 

[danh]

I've read so far that the new one isn't any better as far as that goes. I've also read to turn the alarms off.. which I did. It was alarming constantly because it's not even close. Refractometer says it's fine. I may need to calibrate mine again...

 

[bcavalli]

That's disappointing. I was hoping the new included version would be accurate.

 

[danh]

Did you make sure to separate your probe and power cords?

 

[Adam]

Yes, I ran all of the power cords through 1-1/2 PVC and all of the probe wires through separate 1" PVC pipe. I made sure that where they cross it's at an angle and not parallel. The only other thing I might try with routing them is to lower the 1" pipe to make a little more distance between them.

After setting up Ricky's Apex last night I may calibrate this probe again. His came out within a few tenths of 35 once it was installed in his sump.