Q: about how to read /use refractometer

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Aquarium Advice Activist
Sep 6, 2008
Hi again,

I have the $41 dollar model from Dr. F/S , should be the same as any though. When I look through the eye piece I will sometimes see a very thin white line just a hair above the bottom of the blue area. I believe it is more noticeable when there is more water on the plate. Usually when I see it the blue doesn't have a crisp bottom edge. I am putting 3 or 4 drops on the plate to cover the entire plate , and sometimes gently press down on the clear plastic cover to disperse it evenly on the whole glass plate. The white line would make it read about .001-.002 higher than the bottom edge of the blue. Again the white line isn't always there, and my progressive bi-focals make it that much harder to read.
Any help on how to use this instrument will be useful, ie. Light source, amount of liquid, cleaning instructions, and common mistakes.
This is how I use mine - put 4-5 drops of RO on the plate, lower the plastic top and let the excess drip off (make sure there are no air bubbles), wait 30 seconds for the temperature to come to room temp, look through the refrac against a brightly lit window or lamp and use a tiny screwdriver to move the blue/white line to exactly 0 ppm, dry off the plate and add 4-5 drops of tank water, lower the cover, let excess drip off, wait 30 sec, and look against bright light. Does that make sense? I do find that I have to calibrate it every time I use it because it seems to change on its own sometimes...
Thanks, yours might not have the thin white line that I see, but I'm glad to know you have a fair amount of water on it too. About calibrating every time, is that normal? anyone else want to tell me their experience with that. Is that something that varies from model to model?
You shouldn't have to calibrate a refractometer every time. I've only had to change the calibration on mine once over two years - and I check it every 3 months or so.

I pretty much do what sooju mentioned, except that I kind of press down firmly on the plastic top to "smoosh" the water out, making sure there aren't any air bubbles. Seems like when I don't "smoosh", I get a fuzzy line - kind of like you mentioned Joey.
Ok thanks,

Seems pretty straight forward, I just don't want to make any mistakes with the low gravity it requires to rid Ich. 1.009 dead Ich, 1.007 dead fish, big difference .
I know it sounds crazy, but I do calibrate my refrac every time because it moves around slightly, and I need exactly 1.009 for my hospital tank. Sometimes it stays correct, and sometimes it is slightly off, but either way I no longer trust that it will be accurate unless I calibrate it.
I agree, I mash the top down to get any bubbles out.
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