Help interpenetrating conductivity probe trends

[reefinmike]

Hey all, I have finally seen some success after calibrating my apex's salinity probe for the 4th time. If you care to see the troubles I was having, you can see them here http://www.reefcentral.com/forums/showthread.php?t=2682223. My salinity(conductivity, I know...) probe has showed somewhat promising results since re-calibrating 8 days ago however I am curious about some trends I am seeing. It seems to be trending upwards and I'm also seeing a fairly predictable dip every day from 5/6pm to 1/2am. I'm fighting low PH from high household co2(windows open weather the past two days!!) but the change in PH through the day seems to correlate with the drop in salinity. My kessils are on from 2pm-2am, two sets of t5 turn on 6-9pm and 9pm-1am. This also seems to coincide precisely with the dips. The ballasts and associated wiring are on top of my canopy and a minimum of two feet away from the probe wire. My ATO solenoid also tends to be off 8pm-12a. My water level remains very consistent, my ato kicks on about once an hour adding ~4 ounces at a time to a 110g system. The systems temperature remains pretty consistent within a .5F range with the heater kicking on 6-8x a day tending to be off between 6pm to 3/4am. The temp while the lights are on doesn't rise above the max hysteresis the heaters heat the tank to the rest of the day. The only other electronic on a predictable schedule is the fuge light and UV on from 2am-2pm. The probe is not in the same sump compartment as the temp probe, I put it in a dark corner of the fuge because there are no bubbles and it's furthest away from other electronics/cords there. The fuge currently struggles to keep a golf balls worth of cheato alive in a super low nutrient environment so I wouldn't think it would have to do with a sudden jump in fuge PH.

Any opinions on what could be causing the predictable dip? anyone else experiencing their probe readings slowly creeping up over time? I sure hope the probe will "settle in" and stop rising. The rising trend did dip last night but that may have to do with a small 7 gallon water change(35ppt) and alk dose I did last night. I would also be grateful for any general tips/advice for reliable, consistent probe readings, probe care and calibration tips/frequency. I was bummed that the apex EL came out literally the day I opened my apex wifi and even more bummed when the only useful perk of my purchase proved to be so unreliable. I would eventually like to tighten the alarm parameters and use the probe as a third layer of safety to my ATO system.

 

[slief]

Probably your tank temps varying which impact the conductivity readings. Overlay the temperature on the graph and post a picture without pH but with temps.

 

[neilp2006]

Agree with slief.

if you move your temp probe to the port on the pm2, you can use it to do temp compensation. See if that helps smooth out the curve.


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[reefinmike]

Here ya go! I initially didnt include this graph because while the heater cycles on less frequently when the lights are on, the temp rarely goes above lights off temp. I have the heaters set to kick on at 78.5 and off at 78.8. because the heater is after the temp probe, the tank gets up to 78.9 before it starts falling again. I opened the windows and the house got warmer than usual a couple nights ago resulting in a temp spike but I don't see a corresponding change in salinity.

I also included a picture of my sump setup so maybe someone could propose better probe placement. I dont have the temp probe with the salinity probe because the fuge only gets ~100gph and likely isnt a true representation of the display temperature. I value stable temp in my display more than salinity which only operates an alarm. I know they should be in the same area but it seems that tank temperature patterns have little to do with the salinity patterns. The time the fuge light and UV(on fuge feed) doesnt seem to match up either. especially considering I kept the 30w fuge LED off the last two days. The only thing that seems to line up is that the drop occurs during the period of maximum lighting(/Ph). I tend to feed and swap the filter pad(on top of eggcrate in pic) around the beginning of the salinity drop. I keep a filter pad after the last baffle and as it collects gunk, the water level rises in the last "baffle", sometimes overflowing it. When I swap the filter the sump level is a little higher than usual and hence the ATO being off the next 4-6hrs. If anything I would think the salinity wouldn't have a sudden drop at this moment rather slowly peaking upwards the next several hours as excess water in the system evaporates.

As for the sump- water from the full siphon drains into a raised skimmer compartment. the right side is a half inch higher so water drains left down through the bioballs and baffle system. The bioballs do a wonderful job eliminating microbubbles and dont seem to catch too much crud. I know I should have my filter pad before the bioballs but I will wait until my still maturing system sees any trace of nitrate. I have the temp probe in the skimmer box to get the most accurate display temp, one heater inbetween baffles and a second in the pump compartment. The return sends ~100gph through the UV and to the fuge. The conductivity probe is in the front left corner of the fuge. My Ph and ORP probes are in between baffles. I would have the conductivity probe there alongside it but I worry about electrical interference. I am replumbing the tank shortly to move the UV behind the tank feeding into the display for more efficiency and to reduce flow fluctuations(herbie drain)

kinda baffled on where to put both probes... Ideally I would have two temp probes but I cant yet justify $130 for a PM1 and temp probe. Sure wish apex included a second temp probe and/or made a temp probe module

 

[mcgyvr]

This is why I don't have a salinity/conductivity probe..

It causes you to overreact and attempt to fix/solve what isn't a problem..
There is zero reason to do anything even if your salinity is actually changing from 1.0258 to 1.027 on a daily basis..

Looks to be following temp in some way there..

Just a case of too many gadgets in my opinion..

 

[reefinmike]

mcgyvr- I always appreciate your short blunt answers! Yes I know I am over complicating things with all the gadgets and over analyzing but I have not taken any actions based on the probe readings nor do I plan on having it control anything aside from an alarm/notification if it gets way out of whack. I really just want to get reliable consistent readings


I believe I may have figured out what is causing the sudden dip. This morning I flipped on the T5's to flip over a snail and I happened to notice the reading on my display dropped nearly instantly from 35.8 to 35.2. Lights off and it jumped back up. This coincides with the time the T5's are on, sometimes I keep them on a bit longer so that explains the slight variance. The plugs going to the t5 ballasts are about a foot away from the apex brain and that is the closest the probe wire comes. I believe it may have something to do with stray electricity in the water. Sometimes I get a very faint tingle when my arm is in the water and touches the reflector. Months ago I made sure the ballasts were properly grounded and installed a GFCI which isn't tripped by this.

Is my thinking right? is the stray electricity up in the display causing the readings to drop all the way down in the fuge? maybe a grounding probe is the solution or connecting the ground on the ballast to my reflector?

 

[mcgyvr]

Yes.. Sorry for not stating it earlier...Those probes are highly susceptible to local electrical fields/interference...There isn't much you can do besides physical separation and possibly trying some ferrite clamps on the cable... A ground probe may help but I kind of doubt it..
Wearing a tin foil hat during calibration will help too.

 

[n2585722]

Is the probe in the sump or the tank?

 

[reefinmike]

Is the probe in the sump or the tank?

I mention that in my first post and illustrate it in the second post. It is in a corner of the fuge furthest away from any other wires/electronics.

mcgyvr- Yes I was aware the probe is susceptible to interference from other wires especially ballasts but I never even thought about the stray electricity affecting it! I can live with predictable swings and somewhat minor variations throughout the day but the trend I saw before seems to be continuing. each day the reading rises more and more. It started out peaking at 34.7 and over ten days it has risen to 35.9. I will take some measures to eliminate the electrical interference and completely block all light getting to the probe before I go barking up neptune's tree. I want to be sure I've taken all possible measures before demanding a replacement probe.

Edit: would increased alkalinity cause a significant rise in conductivity? I increased my alk from 9.5 to 10.5 yesterday which coincided with the biggest jump

 

[n2585722]

OK, I assume this is a new probe. Wait a few more days and calibrate again. New probes can drift for awhile until they get acclimated to the tank water. Also temp changes will have an effect on the probe reading. When calibrating make sure the temp of the cal solution is the same as the tank and make sure any air bubbles are out of the probe. The probe has temp compensation and uses the temp probe for the compensation. Set the probe at an angle with the hole in the side of the probe on the high side of the probe. Tap the probe with you finger to dislodge any air bubbles. Also when you place the probe back in the tank tilt the probe at an angle with the hole in the side on the high side. Then tap it with your finger to get any trapped air out. Leaving the probe tilted with the hole on the high side will help keep the air from accumulating in your probe.

 

[n2585722]

I mention that in my first post and illustrate it in the second post. It is in a corner of the fuge furthest away from any other wires/electronics.



mcgyvr- Yes I was aware the probe is susceptible to interference from other wires especially ballasts but I never even thought about the stray electricity affecting it! I can live with predictable swings and somewhat minor variations throughout the day but the trend I saw before seems to be continuing. each day the reading rises more and more. It started out peaking at 34.7 and over ten days it has risen to 35.9. I will take some measures to eliminate the electrical interference and completely block all light getting to the probe before I go barking up neptune's tree. I want to be sure I've taken all possible measures before demanding a replacement probe.



Edit: would increased alkalinity cause a significant rise in conductivity? I increased my alk from 9.5 to 10.5 yesterday which coincided with the biggest jump

I guess that could be possible since you are adding it to the tank. That probe actually measures conductivity or resistance of the water. Anything added that would decrease the resistance will raise the reading.



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[reefinmike]

yup, the probe is a month old. I'm already on calibration #4... each time the probe was in tank water 7-10 days before drying and calibrating again. Today is day ten and the salinity continues to trend upwards. I have done ample homework on proper probe calibration, isolating probe and wire from electrical interference/ballasts, heating calibration solution to tank temp, keeping temp probe in same area(at least during calibration), being sure to purge all air from the probe etc etc. I found some tip on youtube where you fill a probe tip keeper bottle with the calibration solution so you can completely invert the probe, shake and purge all bubbles.

I'll just have to find a way to solve the stray voltage, keep consistent parameters and re calibrate one last time before contacting neptune.

 

[n2585722]

A way to test if it is stray voltage is to get a glass or cup with some tank water in it and place the probe in there and compare the reading in the glass or cup to the reading in the tank. The glass or cup will isolate the probe while it is in the glass or cup. If that is not it then you may want to contact Neptune about this.


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