Calibration fluid

Smitty

Smitty

Premium member
What's up guys, just wanted to share my experience with you all. I ordered a bottle of calibration fluid from marinedepot.com last week to double check my salinity level. I usually calibrate my refractometer using ro/di water and my salt level is always 1.026...but today, I calibrated my refractometer with the calibration fluid and found my tank salt level to actually be at 1.030!!! I'm doing a water change right now as we speak to start bringing that salinity down. Just wanted to share that with everybody, and offer some calibration fluid to those near me who want to double check their refractometers too.
 
After reading the other thread on using calibration fluid, and subsequently buying calibration fluid - I found out the same with my setup! Good call on making it available for others too. If anyone wants to check their meter up north of the city, let me know.
 
Does that mean Ro di water is not 1.00 SG or refractometers dont read water properly ??

also how do we know that the calibration fluid thing is right ??
 
I also bought it from marinedepot two weeks ago. I was using ro/di water before n thought maybe it might be off. After using the calibration fluid. Found out that using ro/di water is the same but at lease I have peace of mind.
 
does it matter if the refractometer is from MarineDepot and says "specifically calibrated for aquarium use" in it? I swear the instructions say to use RODI and set it at 0. I'm always at 1.026 and if it goes lower I can see it in my tank (recently a common experience with this move and some ATO issues). When I bring it back to 1.026 by my refractometer everything gets noticably happier. I hesitate to change what's working, but maybe I've built up a higher tolerance/requirement in my stock over time? Lowering it appropriately might even save on salt LOL.
 
I'll add another option, the Tropic Marine high precision floating hydrometer. You can find them online for $30-40. While this is not lab certified it is accurate enough for our purposes. It has large graduations so it is easy to determine your salinity. I mix up a new batch of water to 1.026 with this and then use it to calibrate by refractometer and salinity meter.

Just a note, floating hydrometers are calibrated at a fixed temperature. A quick google search provides lots of links to temperature/salinity conversion calculators.



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I agree with Herbie, when my tank strays to 1.024 or lower, i can definitely notice my corals arent as happy. bump it back up to 1.025-1.026 and everything is all happy again after the next few days.
 
I would make sure that your RODI water is 0 TDS, I woulf think if it does have a little TDS it would have an effect on the SG. That being said, I got some calibration fluid a while back and found I was a bit off as well.
 
Even when I calibrated it using ro/di water, i was getting a reading of 0 also, and I thought ro/di water was sufficient according to some people and even directions too. The solution I purchased is calibrated to 35ppt/1.026 sg. Although, I think that temp does play a role with water, I don't think the temp is a issue with the fluid.
 
gig said:
I would make sure that your RODI water is 0 TDS, I woulf think if it does have a little TDS it would have an effect on the SG. That being said, I got some calibration fluid a while back and found I was a bit off as well.
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Yep, my tds still reads 0 output, and surprisingly, the input tds is between 4-7.
 
I bought my refractometer from Amazon a few months ago and haven't touched the calibration screw since it seemed right on. As in a 2 gallons of water and 1 cup of instant ocean salt reads 1.026 SG / 35 ppt.
 
FishBeard said:
I agree with Herbie, when my tank strays to 1.024 or lower, i can definitely notice my corals arent as happy. bump it back up to 1.025-1.026 and everything is all happy again after the next few days.
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I agree also, that's how i knew something was off the last 2-3 weeks with my tank, my lps', especially my duncan hasn't been opening up fully.
 
Smitty. Make sure you calibrate multiple times with the calibration fluid. When I calibrate, I usually have to do it multiple times to get it calibrated acurately. The first time is usually off because the temp of the refractometer and calibration fluid are not the same.
 
Again, this is why people need to stop recomending RO/DI and distilled water to calibrate their refractometers. Friends don't let friends kill their reefs!
 
KeishaKornbread said:
Again, this is why people need to stop recomending RO/DI and distilled water to calibrate their refractometers. Friends don't let friends kill their reefs!
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Sometimes in a pinch, u gotta do what u gotta do. at least RO/DI calibration is better than throwing darts wearing a blindfold, or however that line goes...
 
ColaAddict said:
Smitty. Make sure you calibrate multiple times with the calibration fluid. When I calibrate, I usually have to do it multiple times to get it calibrated acurately. The first time is usually off because the temp of the refractometer and calibration fluid are not the same.
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HA!!! I just found that out...literally. I tested 3x's and it actually was 1.028, not 1.030. I also made sure i wiped the glass off with a fresh piece of napkin and clean water, instead of just wiping it off with the same towel. I "may" have had a lil salt residue on the glass screen when I first tested.
 
you can actually watch the reading change as the temp of the liquid reaches the temp of the refractometer. I may have a slight advantage because my refractometer is always in the basement in a dark and cool drawer. If someone else was keeping their refractometer in their cabinet or out in the light it could cause a wider variance and maybe bigger problems. I think I will buy some cal fluid and see if I can do a comparison to RODI for acuracy. if your water reads 0 TDS and you have the temp the same with the fluid and the refractometer what could cause 0 to be wrong, but 1.026 to be accurate? Math is math. I think I must be missing something with the calibration fluid science. I know people have bombed their tanks from this, but wouldn't there have to be another variable that wasn't considered? Sure the cal fluid removes that potential variable, but is it possible to have a problem if the variabbles are controlled? It's not like the scale changes on the refractometer.
 
Smitty said:
HA!!! I just found that out...literally. I tested 3x's and it actually was 1.028, not 1.030. I also made sure i wiped the glass off with a fresh piece of napkin and clean water, instead of just wiping it off with the same towel. I "may" have had a lil salt residue on the glass screen when I first tested.
Click to expand...

Yeah. I usually re-calibrate until the number doesnt change anymore. Alot of times, the first and 2nd time I calibrate give different numbers.
Its the same thing when I check my tank water. I make sure to repeat the test more than once until the number stops changing.
 
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