Check Your Refractometers!!

[jeffbrig]

This is my public service announcement for the year.

Information distilled from Randy's thread in Reef Discussion:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=967301

If you are using this popular $45 refractometer:

You MUST make sure it's calibrated against a known reference at the salinity you intend to be measuring with it. Refractometers calibrated to 0 using RO/DI water (as stated in the instructions) may have SIGNIFICANT ERRORS when measuring at normal saltwater levels. Randy's thread has a link to an article that gives DIY instructions for a 35ppt reference fluid, or you can order 35ppt Pinpoint salinity calibration fluid from several vendors. These match NSW, and can be used to accurately calibrate your refractometer for use in measuring salinity in your tank.

I just used Randy's DIY fluid to test my own refractometer. It read HIGH by .003. :eek1: :eek2: :eek1:

Also, note that one of these refractometers properly calibrated at nsw levels (1.026) will be inaccurate when measuring hyposalinity levels (1.009).

 

[Bullredchaser]

I guess you really do get what you pay for.Several years back some of the club members had issues with some of the cheap refractometers that where selling then sometimes as low as 36.00.They would stay calibrated at a certain specific gravity but be off at another.Lucky for me several of the members at the time swore by the Milwaukee brand.Not only was it accurate right out of the box but I continually check for accuracy using solutions and it's dead on even today 3 years later.I paid more than twice as much then as the cheaper 36.00 model but mine is actually accurate and I can trust it without a shadow of a doubt.It's amazing how much money the club has saved me even if the advice was to spend more money on a higher quality product.

 

[Rogger Castells]

Thanks Jeff, This is real useful info! specially since I have one of those units.

 

[r00onmac]

i do as well and couldnt figure out why LFS water was all showing up at 1.028 ... this shows me that most likely the water is between 1.025 and 1.026 and having calibrated my refractometer at 0 makes it read incorrectly... i dont have the ability to make calibration fluid (ive been diagnosed with laziness) and i cant afford calibration solution (im a college student) but its good to know that if i keep my tank at 1.028 its really at a good SG... lol

 

[Ryanqk]

bullredchaser what model refractometer do you use? do you know a link to a site that sells them? i want to get one and was going to order the cheap one shown above but since christmas is coming maybe i will put a good one on my xmas list.

 

[jeffbrig]

I gave up on the refractometer, and ordered a Pinpoint salinity meter today from Aquatic Eco. $115 for 1, or if you get a few people together, they lower the price to $98 for 3 or more. To me, that's competitive with the price of better refractometers.

 

[bckane]

<a href=showthread.php?s=&postid=8515733#post8515733 target=_blank>Originally posted</a> by jeffbrig
I gave up on the refractometer, and ordered a Pinpoint salinity meter today from Aquatic Eco. $115 for 1, or if you get a few people together, they lower the price to $98 for 3 or more. To me, that's competitive with the price of better refractometers.

Im buy one for $98......anyone else.????

 

[jeffbrig]

I want a finder's fee if you get 3 together.

 

[Pico Keeper]

WOW!

I had been using an electronic salinity meter to keep my tank at 1.026 since it's inception. The other day I used one of these things that belonged to a friend and it read 1.032, I flipped out and started reducing salinity. Now I have to bring it back up, I actually though the electronic monitor was inaccurate.

 

[Ryanqk]

jeffbrig where did you get yours? and what model is it, if its competitive that may be a better choice, does it require calibration?

 

[jeffbrig]

Pinpoint only makes one model of "salinity meter". It does require an inital calibration, which they provide a reference 53mS fluid for. The probe does not degrade like a pH probe, so I don't know to what extent future calibration is required, I would imagine it would be very infrequent.

Be warned: They also sell a similar looking conductivity meter targeted for measuring hardness in freshwater tanks, it does not read the correct range for saltwater.

I purchased mine from Aquatic Ecosystems, because they're in Orlando and ground shipping only takes 1 day. I would post a link, but I don't know if that's kosher for non-sponsors.

 

[kimbertent]

has anyone used the sybon refractometer? i need a refractometer asap (i have ich and was planning on doing hyposalinity) and was looking at this one in the store.