True seawater refractometer?

[Randy Holmes-Farley Verified Community Expert]

So it's really only a tiny bit off when calibrated to 35ppt right? At least that's what I remember from your article

If calibrated to 35 ppt, it will be perfect at 35 ppt.

If calibrated in RO/DI, and if it is otherwise made perfectly as a brine refractometer (may be a risky assumption for a cheapo device) then it will read 33.3 ppt seawater as if it were 35 ppt.

 

[Randy Holmes-Farley Verified Community Expert]

What are the critical or safe boundaries regrading salinity in a reef aquarium? and how does this effect ones consideration with regards general accuracy when purchasing test equipment. ?

I was of the understanding that a range of between 29 ppt to 39 ppt was within a safe boundary. ?

Just for sake of interest, I like to have a robust piece of test equipment if possible. I liked the DD refractometer (around £45) and for my shop I used the Hanna HI 933000 conductivity meter (around £600). I also had a range of calibration samples.

Hobby kit tends to get thrown around so I advise a robust bit of kit that is within budget. Automatic temp compensation and a clear reading scale may also help.

The TMC refractometer mentioned earlier I had a number of these returned to my store broken, I stopped selling them.

I still don't understand why some people calibrate their refractometer at 0. I always use 35ppt. Can you shed some light on this @Randy Holmes-Farley

Fortunately for reefers, a wide range seems fine. I'm not sure it is as wide as 29 to 39 ppt however.

People calibrate many refractometers at 0 ppt because the manufacturers used to always say to do that. It is not good practice in general to calibrate so far from the desired reading, but would work if the device is a perfectly made seawater refractometer. It is not a good plan for reason of imperfect manufacture, and in some cases, not knowing if it is a brine or seawater refractometer.

 

[I never finish anythi]

I'm on my phone at the moment so this is a screenshot of one but I can post a link in a bit.

I have it and honestly mine is pretty accurate . Tested against my lfs digital and it is bang on . And holds calibration well.

 

[D3DPrintedThingz]

I used that refractometer for the first 8 months , calibrated it with RODI and ran at 1.026.

my LFS keeps their tanks at 1.020. My levels for calcium and magnesium were super low, for 8 months. On a hunch I tested LFS water and it was 1.026. So by that logic I was 0.006 ppm off when calibrating with RODI.

after about 3 months of using Hanna salinity meter,, tank looks 100% better. My personal experience is very negative when using RODI to calibrate a refractometer to 1.000

 

[Tony Thompson]

Fortunately for reefers, a wide range seems fine. I'm not sure it is as wide as 29 to 39 ppt however.

People calibrate many refractometers at 0 ppt because the manufacturers used to always say to do that. It is not good practice in general to calibrate so far from the desired reading, but would work if the device is a perfectly made seawater refractometer. It is not a good plan for reason of imperfect manufacture, and in some cases, not knowing if it is a brine or seawater refractometer.

My range is calculated from my basic recollection of average salinities on a range of natural coral reefs which has corals thriving in salinities even further outside that range, I just took an average for safety margins. I may be wrong.

I understand the guidelines often cited in the hobby as a precautionary practice.

I am interested in investigating many of the "hobby" guidelines and how they can sometimes become thought of as critically important with regards accuracy. I feel this also plays into the hands of some manufacturers.

My personal aquariums are an extension of my fascination with marine biology (on a novice level). I understand the peculiarities of closed systems however I often find some of the common statements found in the hobby to be contradictory to basic biology.

Even the basic parameters of Salinity, Alkalinity, Temperature, Nitrate and Phosphate, I feel sometimes create a form of obsession for a set figure with some reefers.

One of the reasons I miss some of the older type of online reef magazines that yourself and others contributed to. I find those articles much more detailed and in the same way holistic in their content.

Best wishes to you Randy.