Troubleshooting refractometer

[treesprite]

What kinds of problems can make a refractometer give inconsistent readings from one minute to the next? 

 

I can't find my calibration fluid, but even using just RO, the reading should be consistent for the same batch of water tested a few minutes apart so there is no temperature variation. 

 

A side question is, does RO really have a true 0 reading on a calibrated refractometer? I've never compared so I have no idea. Not knowing makes me not trust using the RO. I did just get new filters from AWI.

 

Info is appreciated. 

Edited January 27, 2020 by treesprite

[treesprite]

I went ahead and ordered a new one and calibration fluid. The new one is kind of cheap, but I'm hoping I can figure out what is wrong with the one I already have. Still, I need to know what the possible problems are so I know what to look for.

 

 

[Origami]

Depending on the refractometer, you can't really use RO/DI to calibrate. Most of the inexpensive ones are brine refractometers that you are better to use a 35 ppt seawater reference to minimize slope and offset errors near the point of testing (that is, near your tank salinity). Deltec marketed a refractometer years ago that had a scale calibrated for the hobby. In that model, you could use pure water for calibration.

[Origami]

Possible problems include loose comp end inside. This might happen if you were to drop it. If the cover slip did not lie flat and parallel to the sample plate, there might be some added error, too.

[treesprite]

6 hours ago, Origami said:

Possible problems include loose comp end inside. This might happen if you were to drop it. If the cover slip did not lie flat and parallel to the sample plate, there might be some added error, too.

 

Thanks for the response, Tom.

 

It may be the cover not laying flat every time. The cover isnt hinged directly to the body, it is hinged to another piece that is hinged to the body, which complicates any laying flat issue.

 

I don't think I've dropped it, but can't be sure.

 

The one I ordered says it is for marine, sea water, aquarium. I don't know about the one I'm already using, which doesn't have a brand name on it (I either bought it from a DC MACNA vendor or someone brought it to MACNA for me, because a few days earlier I dropped the previous one into my Brute full of water).

 

I read a lot of stuff the last couple days about using RO/DI water being bad. I usually use calibration fluid but can't find it anywhere. 

 

2 new astrea snails died recently, which I'm worried is the result of salinity being off. They could have died because astreas can't flip themselves (both were on the sand when found dead), or could have been unhealthy when I got them.  Corals seem okay except for some palys that started having issues after a lighting change that made them umbrella, so I moved them but now they  shrunken and thinned out.... could be the lighting or could be salinity, or both, or maybe something unknown. 

 

 

[Origami]

Forrest, this may still be an option. Years ago RHF put this article together enabling our making homemade references adequate for our hobbyist use.

http://reefkeeping.com/issues/2004-06/rhf/index.htm

[ScooterTDI]

I've found that temperature to be the primary driver of variability like you are experiencing. If the refractometer, tank water, and calibration solution are at different temperatures, you are likely to experience measurement errors. For instance, if your refractometer and calibration solution are colder than the tank water, then the tank water may initially appear lower salinity than it actually is. As the refractometer cools down the tank water on the slide, the salinity will appear to increase as the density of the water on the slide increases. Recalibrating and re measureing multiple times while the temperature is unsteady can cause the apparent salinity to jump all over the place. The refractometer are advertised as being automatically temperature corrected (ATC), but I think this is just relying on the mass of aluminum around the stage to act as a heat sink and requires enough time for the temperature of the sample to equilibrate with that of the refractometer and assumed that the refractometer won't change temperatures substantially when handling during measurement.

 

These issues can be avoided by either 1) storing the calibration solution and refractometer at the same temperature as the tank ( much preferred) or 2) at least letting the calibration solution and sample water sit on the slide for long enough to equilibrate temperatures.

 

I used to have lots of problems in the winter when I was mixing saltwater in an unheated laundry room. When mixing, the water, calibration solution, and refractometer would all be quite cold. Then I'd heat up the water to tank temps, but still measure with a cold calibration solution and refractometer. This yielded a lower salinity than obtained at mixing. Then I'd add some salt to adjust and bring the water upstairs and compare to the salinity of the tank and it would be totally off (and changing over time as the temperature of the refractometer changed.) Now, I just store everything near tank temperatures and the refractometer calibration holds very well over long periods.

[treesprite]

 

So, the new one is here, giving me a way to evaluate the old one. The one on top is the new one. The one on the bottom - which you can see has a gap - is the old one. They both have the second hinged black piece. On the new one, both the black piece and the clear piece move freely and fall into coordinated place so the clear piece can lay flat with ease. However, on the old one, the hinges on both pieces are stiff and make the pieces stick in positions that cause the clear piece to not lay flat unless I fiddle around with it .... I'm sure the time spent to do the fiddling, the fiddling itself, and the piece not always laying flat are affecting the samples and the reading of the samples.

 

I'm wondering if I can loosen the hinges up using vinegar or alcohol. I could try WD40, but I'm worried about using something toxic like that on an aquarium tool.

 

I'm in a hurry to calibrate and use the new one, but both the tool and the fluid are super cold from sitting outside of the door. 

 

Oh, the directions say to calibrate with distilled water.

 

 

 

 

 

Edited January 29, 2020 by treesprite

[treesprite]

 I calibrated the new one and used it. Tank water 37ppt and new mix 38ppt. I'll have to get out some buckets because the Brute is completely filled with no room for fresh water. How bad is it for the tank water to be at 37? I'll slowly adjust it, but I don't know how long it has been high.

Edited January 29, 2020 by treesprite

[ImGoingCoastal]

Something that I've done in the past is tank some tank water, and your refractometer to a friend's house and test against their refractometer.... Also an option is to take it to an LFS and ask them to check it. Supreme Reefs did mine no problems. Even adjusted it for me.

Sent from my SM-G970U1 using Tapatalk

[treesprite]

1 hour ago, ImGoingCoastal said:

Something that I've done in the past is tank some tank water, and your refractometer to a friend's house and test against their refractometer.... Also an option is to take it to an LFS and ask them to check it. Supreme Reefs did mine no problems. Even adjusted it for me.

Sent from my SM-G970U1 using Tapatalk
 

 

I don't know of any reefers in my immediate area, or whose schedule would match up with mine. There was a time that I went to a past WAMAS member's house to show her with a refractometer how insanely high her salinity was. She was just using a hydrometer and her livestock was dying. She's not in the hobby anymore. 

 

The closest LFS is one I wouldn't trust with anything that has to do with livestock survival. I only ever go there on rare occasions if I need some piece of something or gadget, because they have a lot stuff that most places don't sell. 

[GraffitiSpotCorals]

Also the glass on the refractometer can become loose or bad. Had a friend who crashed a 300 gallon because his glass was old and corroded Around the seal from use. 
Like said above only use 35 ppt calibration fluid and I even buy it every year because it would go bad eventually from use. 
Also calibrate everytime you use it. 
I moved to using a digital one so I could use rodi. It’s much easier although I still don’t trust it fully...

[treesprite]

3 hours ago, GraffitiSpotCorals said:

Also the glass on the refractometer can become loose or bad. Had a friend who crashed a 300 gallon because his glass was old and corroded Around the seal from use. 
Like said above only use 35 ppt calibration fluid and I even buy it every year because it would go bad eventually from use. 
Also calibrate everytime you use it. 
I moved to using a digital one so I could use rodi. It’s much easier although I still don’t trust it fully...

 

I'd like to get a digital, but can't afford it right now. I have to keep tank stuff on hold until I know definitively whether I'm moving to Middle of Nowhere.

[GraffitiSpotCorals]

Yea i has to hold off for a while too. But variations between refractometers results and swings on the same test water were killing me!  Finally I just got one and don’t bother testing with any second test for verification like I was before. I just double check it with regant sometimes and if it’s a point off or right on I am ok with it. 

[malacoda]

If you're trying to save the old one, I would suggest trying to clean out the hinges with hot water. Work the hinges a bit while holding it under faucet. From what I've seen, the primary cause of hinges 'sticking' is trace amounts of salt build up.  I'm not sure vinegar would work any better than hot water ... and WD40 may be a little bit of a pain to completely clean off the glass plate and plastic cover.

 

While it's unlikely, there is also the possiblity the plastic lens has warped a little with age.

Edited January 31, 2020 by malacoda

[treesprite]

Thanks for the responses.

 

The warping has also occurred to me, but seems unlikely because out hasn't been exposed to excessive temperatures or pressures.

 

GraffitiSpotCorals,

which one did you get? I'm wondering if the lower priced Milwaukee one is just as good as the higher priced models. It seems people had complaints about a Hanna model, but I can't remember the specifics.

[GraffitiSpotCorals]

I think they are the same thing basically just rebranded, from what I heard.  I have the milwaukee ma871. 

[Origami]

I have the Milawaukee, too. I also keep two refractometers on hand. I've pushed the hinge pin out of a refractometer when replacing the cover plate once. It's not terribly difficult to do. A small drop of WD40 on each end, worked in, would probably work just fine and would be a cheap way to do this. (Spray some in the WD40 cap and use a toothpick to precisely place the oil so the optical surfaces remain clean.)

 

I could probably make up a little fluid that you could use to calibrate your refractometer, Forrest. Will you be at the meeting?

[treesprite]

7 hours ago, Origami said:

I have the Milawaukee, too. I also keep two refractometers on hand. I've pushed the hinge pin out of a refractometer when replacing the cover plate once. It's not terribly difficult to do. A small drop of WD40 on each end, worked in, would probably work just fine and would be a cheap way to do this. (Spray some in the WD40 cap and use a toothpick to precisely place the oil so the optical surfaces remain clean.)

 

I could probably make up a little fluid that you could use to calibrate your refractometer, Forrest. Will you be at the meeting?

 

Thanks, Tom. I got some calibrating fluid in the order with the refractometer.

 

Last night I was digging around for a PVC piece, and to my surprise I found an ancient Instant Ocean hydrometer. It has a faded note with a line written on it,  to indicate that 1.025 was reading 1.028. It is slightly more off now, just sitting in a mess of junk for I don't know how many years.

 

After getting my tank salinity back to normal, I mess d it up again. Last night while I was doing stuff behind the tank, the ATO container ran out so I filled it, even though I thought I filled out the day before.  This morning the carpet was all wet so I was frantically looking for something leaking when nothing was leaking. Then I realized the ATO water was empty again. I had knocked the ATO line out of place, so the tank was getting lower which just kept the ATO running all night. 10 gallons of water on the floor (container holds 5). Now my salinity is 36.

 

Most of my snails have now died, including the ones I had before I got the ones I thought might have been a bad batch. No problem with the corals except some palys that started looking bad but those are perking back up. No problems with the fish.

Edited February 1, 2020 by treesprite

[treesprite]

Crap. Just found my blenny dead. A few hours ago he looked fine, was acting normal. I'm guessing the salinity changes got to him after all. The only other fish I have is an orchid dottyback, which is eating fine and looks fine.... I hope it stays that way. 

[treesprite]

Now my dottyback has been unseen for a couple of days. It mostly only comes out at feeding time, but hasn't even done that. I'm guessing it died in its hidey hole. Poor fish. 

[robertmi]

Hello,

As for the calibration fluid, to keep it good and accurate for a long time don't forget to keep the lid tight and try to have the lid off for as little a time as possible. The main reason for calibration fluid going bad is due to evaporation and the reading (ppt) drifting high.

[treesprite]

15 hours ago, robertmi said:

Hello,

As for the calibration fluid, to keep it good and accurate for a long time don't forget to keep the lid tight and try to have the lid off for as little a time as possible. The main reason for calibration fluid going bad is due to evaporation and the reading (ppt) drifting high.

 

Good advice.

[davelin315]

Watch out for quality control on calibration fluids.  I recently found that four brands had different readings that were off by a lot.  If I recall correctly Hannah was at the low end, Brightwell was at the high end, and two others were in the middle.  The differences were stunning - a range of 1.023 to 1.029.

 

As far as being at 37 or 38 I honestly don’t believe that is a huge issue.  In parts of the Red Sea I believe salinity is upwards of 40 where fish are collected and reefs are present.  Really it is more about consistency and the variations in different people’s systems is often fairly large.

[GraffitiSpotCorals]

Wow that’s good to know, I thought that a standard is easy to make?  How are these big companies messing it up so bad?  I am wondering if this is what caused me all my pain a few years ago. Just one reason I like my digital one that I can use to water to calibrate successfully.