Please help me urgently!

[Mr31415]

This is ABSOLUTELY CRAZY. I have a 550l reef aquarium and I last did a water change about 3 weeks ago. I have an automated topup system.

Tonight my AquaTronica is showing salinity values from 1.0250 (which it used to be at for the past 3 weeks) going up to 1.0275 in a matter of seconds.... Then down again. So intuitively one might think the probe is faulty. So I take out my refractometer and sample the water. 1.020. Then I sample again - same location. 1.027. Then I clean everything and sample from the sump. 1.020. Clean again and sample from the main display - 1.027.

What is going on!!!! It is IMPOSSIBLE for 550l of water to have such massive salinity deviations. And the chances of both an electronic probe as well as a mechanical refractometer been broken simultaneously is 0.

 

[BlueCorn]

Re: Please help me urgently!

<a href=showthread.php?s=&postid=7991437#post7991437 target=_blank>Originally posted</a> by Mr31415
What is going on!!!! It is IMPOSSIBLE for 550l of water to have such massive salinity deviations. And the chances of both an electronic probe as well as a mechanical refractometer been broken simultaneously is 0.

First thing is to slow down.

It may be unlikely that your probe and refractometer are both faulty, but it's even less likely that your salinity is changing by the minute. Take a sample of your water to a local LFS and have them test it. You might also want to take your testing equipment with you to make sure that you're using it right.

If you try to react to what you're currently seeing, it's very likely that things will die.

 

[Travis L. Stevens]

There is a chance that both of them could be broke. Make sure that your pump to your tank is working decent. I know, far fetched, but it could happen.

 

[MCary]

Weird? Was your auto topoff going at the time? Fresh water entering the sump might account for the difference.

Mike

 

[Mr31415]

All the equipment in the tank is working - have verified just now. Have recalibrated the sensor using the reference solution of 52us - it was 100% correct based on that and at 25C.

Topup have not run in the past 5 hours.

I have done SEVERAL tests now - on the far side of the main tank (i.e. very far away from any new water/sump return feed). The refractometer repeatedly shows 1.020 - the electrode shows 1.025 - 1.027.

How can a refractometer go wrong? It is based on the refractive properties of light entering a medium of different density AFAIK, and that is VERY difficult to go wrong? I never had the refractometer fall or bump.

And I am rather sure I am using the equipment correctly - having a degree in electrical engineering means I understand electronics and physics.

 

[GotSalt?]

why not invest in a cheap bober style salinity tester (sorry forgot what they are called)

 

[theatrus]

Have you calibrated your refractometer? Most have a little screw to adjust, which could have been jiggled.

 

[vessxpress1]

Here's a thread over at the Reef Chemistry forum that we just finished today. Randy has a calibration solution test you can try on your refractometer. I found out mine was reading high and changed it today.

http://www.reefcentral.com/forums/showthread.php?s=&threadid=911123

 

[Mr31415]

Ok that is something I did not know - that one can calibrate your refractometer. I assume (maybe because I have a 2.5 year old daugter who thinks she is a mechanic) that there is a remote possibility she might have inadvertently adjusted it...

I used my reference solution of 52ms/cm @ 25C from the AquaTronica and re-calibrated my electrode again after rinsing it in RO water and drying it. It seems to be *much* more stable now at 1.0244 - I have NO IDEA why it jumped like that. Maybe an air bubble?

Anycase, I used it to test my QT tank's water too and it said 1.0078. The refractometer said 1.004 and 1.020 for the main tank. I.e. it is under by quite a bit. I also tested the reference liquid - at 25C it converts to 1.0244. So I adjusted the refractometer (thanks theatrus) to that value. I retested both the QT and the main and am getting the same results as the electrode now. I guess by both calibrating to the electrode and the density calibration fluid I can be assured that they are both correct now?

It is extremely important since I am doing hyposalinity and I had my tank at 1.005 due to these errors...

At least it is back up close to 1.008 which is better.

And my main display is 1.0244 - not 1.028. Thanks for your help. Let me know if you disagree with what I did here. (I do not have access to the specific brands of salts mentioned in the forum so I improvised).