Scottshopinc
New member
Don't listen to anyone who says you can use rodi water to check calibration like I did. Got my rcs in today and I'm 5ppt off. All this time I've been running at tank at 39-40 ppt. Noob mistake #3735280
Refractometer calibration solution is a must!
- Thread starter Scottshopinc
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Scottshopinc
New member
I too have been doing the same thing. I thought I was all squared away. But after useing this calibration solution I'm off 5ppt. Rodi/distilled always reads zero.
bshow24
Member
There are many reasons where something could turn up incorrect readings, including a damaged/incorrectly manufactured refractometer. Lately, the prices of these things are dropping, but I paid top dollar for mine and made sure it was quality built/tested for this reason. Heck, I still compare it to my LFS every 6 months when I calibrate!
I agree, you can't go wrong with calibration fluid, but it doesn't mean that utilizing distilled/rodi water is an improper way of calibrating.
I agree, you can't go wrong with calibration fluid, but it doesn't mean that utilizing distilled/rodi water is an improper way of calibrating.
Reef Frog
New member
It's been a long time, but the last time I compared RODI with 1.026 reference solution, I think the variance was only about .002 or so. I'll have to remember to check again just out of curiosity.
I was participating in a thread a few months ago with some very experienced reefers who were disappointed with their new refractometers because they wouldn't hold a reading - they felt a good unit should hold the proper calibration for a long time. I have always checked calibration before each use
I was participating in a thread a few months ago with some very experienced reefers who were disappointed with their new refractometers because they wouldn't hold a reading - they felt a good unit should hold the proper calibration for a long time. I have always checked calibration before each use
Scottshopinc
New member
This was first time using the fluid, just lil shocked how off it was. But I'm still learning a lot, my weekly water change is tomorrow, ill trying to bring it down some.
JMorris271
New member
evaporation
evaporation
Doesn't the amount of water lost due to evaporation affect the reading and actually skew things a bit??
Please pardon my hopping onto your thread
evaporation
Doesn't the amount of water lost due to evaporation affect the reading and actually skew things a bit??
Please pardon my hopping onto your thread
bshow24
Member
This definitely affects it based on water volume/how much evap occurs. I remember before I used a sump/ato, my 8 gallon tank went from 1.026 to 1.035 in a matter of 16 hours. My 28 gallon on the other hand was manageable, only getting up to 1.029 max. Still a pretty large change though, hence the sump and ato!
gone fishin
New member
IMO since we are measuring for the 1.026 area of the scale then it makes good sense to use the calibration fluid. We are only able to do a single point calibration so calibrate to what we want to measure. On the hand if one was to be doing hyposalinity treatment for ich then it would be best to use DI water since we are measuring closer to 1.
TangingOut
New member
Make sure to get new calibration fluid each year. My one year old fluid is off according to the new one I just got. I now have it stored in a Ziploc bag.
jason2459
Well-known member
It is improper if you don't have a true seawater refractometer.
http://reefkeeping.com/issues/2006-12/rhf/
There are many refractometers sold to us as aquarium or saltwater or many other things listed leading one tobelieve they are what we truly are testing for. But they are more often then not made for testing brine or brackish waters. Ive even seen one made for urine being sold for fish tank use. If what you have is not a seawater refractometer then calibrating to 0 with distilled water like all their manuals say to do you will be off when trying to test the refraction of our seawater at 35ppt.
However, if you calibrate those with a 35ppt standard then you will be ok. But keep in mind some of those calibration fluids you buy can be off too. Or become off overtime due to evaporation.
Digital scales that measure to the 100th place are becoming cheaper and you can make your own solution as described in that link I just posted.
downbeach
New member
You should be calibrating with a solution that is close to the refractive index of the sample you will be testing, i.e. 35ppt(1.026).
From the article that Jason posted:
http://reefkeeping.com/issues/2006-12/rhf/#13
From the article that Jason posted:
http://reefkeeping.com/issues/2006-12/rhf/#13
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