Go buy a Refractometer now!

[Steemax]

This is more of a PSA.

 

I never thought a refractometer was very useful until today.

I've always used a hydrometer and it has always read my LFS water at 1.019 so I have always added extra salt to the mix.

 

Today I purchased a refractometer for the first time in being in this hobby for 12 years and oh wow!

 

I made sure it was calibrated with distilled water and what do you know, the hydrometer was off by .005!

I had been adding salt and my salinity has been at 1.029. I suppose that's why i've been having issues with my corals not growing and shrinking over time. So now i'll be slowly replacing salt water with distilled water over a period of 3 weeks until it's at 1.024

 

in-case anyone is wondering i bought my refractometer from Amazon for $35+shipping. I made sure it had very good reviews and it was a sinch to calibrate.

[Mariaface]

It's good that you purchased a refractometer, but keep in mind that you're supposed to calibrate to the salinity you want. Invest in some calibration fluid while you're at it, because calibrating with RO/DI water when you're not meant to can cause some slight error in the 35ppt range later.

[Steemax]

It's good that you purchased a refractometer, but keep in mind that you're supposed to calibrate to the salinity you want. Invest in some calibration fluid while you're at it, because calibrating with RO/DI water when you're not meant to can cause some slight error in the 35ppt range later.

Interesting! Instructions call for using distilled water... So it's much better to use 35ppt calibration fluid?

[Addinali]

Depends on the refractometer mine says to use rodi and I have for 5 years now I test it next to the Milwaukee digital at my pet store and its always within .001. But there is refractometers that require the calibration fluid which is a pain but once there calibrated there spot on. Compared to mine which fluctuates from time to time.

[braaap]

Always use calibration fluid. It can be bought on ebay or other reef supply sites for under $5.

[Addinali]

Always use calibration fluid. It can be bought on ebay or other reef supply sites for under $5.

You say always but you don't give a reason why.

At least give us a reason.

[BulkRate]

Long topic short-ish, all refractometers have some degree of error over their testing range. By calibrating yours to a known standard any tolerances of the device's construction or aberrations are minimized - you end up KNOWING that the line shown at 1.026 IS indeed 1.026 and could care less about the zeroing & measurements outside the relatively narrow scale of what you're testing.

 

Most times our water mixes to within .005 of where we want it to be just by following the directions on the box/bag/pail. Most times a refractometer calibrated with a 35ppt reference solution will be pretty accurate within that small a range. Outside a lab and with hobby-grade equipment, that's about as good as it gets and most times is good enough.

 

That's the idea behind it. Now introduce "our hobby" to the picture:

Caps get left loose or off of reference fluid vials all the time and the salinity creeps up in between tests. Said fluid may simply be from a batch that mixed a little high or low. Or accidentally is nothing but distilled water (had this happen twice). Nowadays there's "brine" and "seawater" refractometers and sometimes the companies selling them aren't even sure which one they built, apparently. There's even different calibration standards depending on which of those devices you're using. It is a mess, and any two hobiest asked will likely have three valid opinions.

 

I've had mixed results with 3 different refractometers over the past 3 years. One wouldn't hold a calibration regardless of method used (solution or distilled) (the ATC feature turned out to be faulty from the factory). One was great at first but developed a film over the prism despite kid gloves handling, ending up reading .003 low. And the latest one has just plain worked for the last six months with no fuss using the manufacturer's stated calibration method (distilled) & has always matched when compared with other units at an LFS. All of them cost within a few bucks of each other.

 

Best bet is to find a "good" unit (i.e. reads accurately, holds a calibration reliably - this can vary even between the same make & model... just keep returning them until you get a reliable unit) and choose a decent "middle of the road" salinity to keep your tank at such that 0.001 error won't appreciably make a difference.

[spazizz]

Buy a glass hydrometer now!

 

 

They are consistant, all you have to do is test it against some thing then you're set to go. No need to ever calibrate again.

[Pancetta]

My old eyes has trouble reading a typical refractometer. So I splurged and bought one of these.

 

http://www.marinedepot.com/Milwaukee_Seawater_Digital_Refractometer_Aquarium_Refractometers-Milwaukee_Instruments_Inc.-4M00600-FITEOPRF-vi.html

 

Very easy to read and very accurate. Turns out one of my LFS uses the same device.

[Eisernes]

I use the digital milwaukee too. So much easier to just push the button.

[CrazyEyes]

This is just my opinion, the Milwaukee digital refractometers are nice, they're easy to read etc. I just wish they didn't have a +/- 0.002 range, so if you're mixing your SW at 1.025 it could be 1.023 or 1.026, might not sound like a whole lot but when you're not wanting stuff like CA, ALK etc swinging around it becomes an issue. Just food for thought.

[Mariaface]

I'm considering going digital, actually. If the accuracy's off by that much, would testing repeatedly give you a better idea, or is that just a random range?

[gena]

My old eyes has trouble reading a typical refractometer. So I splurged and bought one of these.

 

http://www.marinedepot.com/Milwaukee_Seawater_Digital_Refractometer_Aquarium_Refractometers-Milwaukee_Instruments_Inc.-4M00600-FITEOPRF-vi.html

 

Very easy to read and very accurate. Turns out one of my LFS uses the same device.

I may have to splurge on one of these someday .

[IzzyTheFool]

My old eyes has trouble reading a typical refractometer. So I splurged and bought one of these.

 

http://www.marinedepot.com/Milwaukee_Seawater_Digital_Refractometer_Aquarium_Refractometers-Milwaukee_Instruments_Inc.-4M00600-FITEOPRF-vi.html

 

Very easy to read and very accurate. Turns out one of my LFS uses the same device.

 

Any opinion on how you would rate this versus the pinpoint salinity monitor?

 

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+27697+28224+4486&pcatid=4486

[TOURING]

Not trying to sound like a dirt bag but how wasn't that one of the first things you bought for your tank?

[Pancetta]

I bought some calibration fluid for my Milwaukee unit and it has been dead on except for one time.

It was off by .001. I cleaned it with RO water and it was OK after that.

 

Personally I was having so much trouble reading the other refractometer that this unit is much more accurate for me.

[Eisernes]

I'm considering going digital, actually. If the accuracy's off by that much, would testing repeatedly give you a better idea, or is that just a random range?

Mine is always dead on with the calibration fluid. Also consider that normally people only change 10% of their water at a time. If it was slightly off by say 0.001 then that small amount of water being off by that small of an amount isn't going to make much difference imo.

[CrazyEyes]

Yeah that's a good point man, not saying they WILL be off but, just something I've always thought about.

[Mariaface]

Mine is always dead on with the calibration fluid. Also consider that normally people only change 10% of their water at a time. If it was slightly off by say 0.001 then that small amount of water being off by that small of an amount isn't going to make much difference imo.

 

Fair enough! Thanks!

[BulkRate]

I commented in another, similar thread... my own MA887 is a bear to keep calibrated, but seems to be more due to my own lab technique (or lack thereof) than any particular defect of the unit itself. Keep in mind that ALL refractometers at the hobby end of the scale are bottom-of-the-barrel quality wise compared to professional gear that costs multiple x's more. Not saying you won't be better off using one versus a hydrometer - just that you could get a unit that works perfectly or one that consistently reads high or low and all of them could have been built in the same lot/from the same manufacturer/at the same facility.

 

If in doubt using your MA887, run three tests with flushes of the well with R/0 & drying between measurements or use a larger sample than the "few drops" stated in some manuals to minimize error due to residue. Best 2 out of three wins.

[Pancetta]

Any opinion on how you would rate this versus the pinpoint salinity monitor?

 

http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+27697+28224+4486&pcatid=4486'>http://www.drsfostersmith.com/product/prod_display.cfm?c=3578+27697+28224+4486&pcatid=4486

 

Izzy,

I have no experience with the Pinpoint unit. I have however read good reviews on other aquarium sites.

 

David

[Steve973]

This is just my opinion, the Milwaukee digital refractometers are nice, they're easy to read etc. I just wish they didn't have a +/- 0.002 range, so if you're mixing your SW at 1.025 it could be 1.023 or 1.026, might not sound like a whole lot but when you're not wanting stuff like CA, ALK etc swinging around it becomes an issue. Just food for thought.

Most of the hand-held refractometers that we use with the prism are +/- 0.005, so these are pretty accurate for the price range. I just got mine recently, and it comes with steam distilled water for calibration, and a 1.025 reference solution. After calibration, it read the reference solution precisely at 1.025. It was consistent with repeated tests of calibration and reading the reference solution. All in all, it seems to be accurate and consistent beyond the specs.

 

If you do get the kind that you look through, though, make sure that you get a seawater refractometer. Apparently, the ones meant for brine give different readings than the ones meant for seawater.

[Tamberav]

Interesting! Instructions call for using distilled water... So it's much better to use 35ppt calibration fluid?

 

No.

 

Some are made for sea water and others are made for salt/brine water. Sea water ones calibrate with distilled/ultra pure water and salt water/brine uses 35ppt.

 

The problem arises when you calibrate with distilled on a salt/brine refractometer.

 

Post #16 if you like learning random things.

http://www.reefcentral.com/forums/showthread.php?t=1933819

[afyounie]

I calibrate my hydrometer with RO/DI per mfg instructions and I do this every month or so because they naturally creep do to changes in temperature, movements, and so on. Its a good idea to calibrate every once in a while. At this point though, I only test for ease of mind because I consistently mix to 1.025 SG with 2 cups of Brightwell salt in a 5 gal bucket. So if I didn't test I'd probably be ok, but then I'd go crazy wondering about all the what-ifs. I probably will never purchase the Milwaukee tester because I'd rather spend that money on a ph probe for my arduino controller, and the refractometer is good enough.

[Saverio]

I calibrated with the 35ppt standard. makes more sense to me to callibrate in the range of what you will be testing. Much like 2pt calibration of a digital pH meter using 7.0 and 10.0 standards.