Got a refractometer and WOW, way out...gotta fix

[Slick Fork]

Unfortunately there's no LFS around that deal in SW stuff. Closest would be Calgary and that's a 2hr drive for me. Are there any other ways I could confirm the reading? Livestock isn't visibly stressed at all so I'm not in a panic, it'll just bug me now that I know about it!

[Reefer Rob]

Stability is more important than the actual level. A reading of 1.030 on the refractometers they sell at J & L is probably about right, as they read high. They also sell the 53 uS calibration fluid.

For more info read this thread

[ron101]

If the readings are accurate and you want to drop from 1.030 to 1.024 you will need to swap out about 25 gallons total (assuming total volume of 125gal) - more if you are doing it incrementally.

If you use RO water you will probably have to supplement more calcium and carbonate additives to keep overall levels up.

[midgetwaiter]

You can make your own calibration solution by following the info in this article:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

You really want to do it with a scale though and make sure you get the solution right. The AMI calibration solution is cheap enough that I wouldn't bother.

My refractometer was pretty good at first but it has been off more and more lately, probably dropped it or something. I was just lucky enough to have heard about the potential problems with the calibration already so I didn't go and screw anything up. If your livestock looks good make sure you can confirm your measurement before you change something.

*EDIT*

I don't like the coke bottle thing in the article and I had a few minutes to kill so I figured out how to make up a decent solution if you don't have a scale but do have a fairly precise liquid volume measure. You need to mix 3tsp table salt in 491ml RO water. Assuming that the tsp of salt measures 6.2g, it should be pretty close, that will give you a solution that should read 35 ppt or 1.265ish.

Turns out the calibration I did to my RHS10-ATC based on a Deep Six hydrometer reading was bang on. Back to the drawer with the refractometer.

[crystalz]

I also started with a hydrometer. Hydrometers shouldn't even be sold as a salt/sg measuring device. My refractometer was a real eye opener for me too. Hydrometer was way out.

[Slick Fork]

Thanks for all the help so far! So I did an improvised DIY solution following the basis of the reefkeeping article. I used 1927ml of RO water, and mixed in 1/4 cup (73grams) of Salt... The salt was easy to measure with a measuring cup and I used another glass measuring cup to get 1900 ml of water, I used a syringe to add the final 27 mL of water so I'm fairly certain I was precise.

I did this mixture 3 times just to be certain I didn't screw up somewhere

Now, just to be sure when he says "Morton's Iodized Salt" he's talking about an American Brand name for table salt correct???

This mixture gives me the 3.65% ratio of salt to water I need to adjust to a 35 ppt reading on the refractometer. I took 3 readings off each batch, every reading of every batch was within .005 of 1.029 so I proceeded to adjust my refractometer to 35ppt or 1.026.

So, with all that done do you guys think I could be confident trusting the reading I'll take after supper?

Thanks and Cheers

[Reefer Rob]

You should get the Pinpoint fluid before you change anything. No rush, corals can thrive in a pretty wide range of salinity... as long as it's stable. If your tank looks good, don't mess with it! Refractometers should sold with a 35 ppt calibration fluid.

[midgetwaiter]

Originally Posted by Slick Fork

Thanks for all the help so far! So I did an improvised DIY solution following the basis of the reefkeeping article. I used 1927ml of RO water, and mixed in 1/4 cup (73grams) of Salt... The salt was easy to measure with a measuring cup and I used another glass measuring cup to get 1900 ml of water, I used a syringe to add the final 27 mL of water so I'm fairly certain I was precise.

Your math is right and the fact you got the same result 3 times is a good sign. It comes down to how precise your measures were, a good scale would work better than volume measurements.

Originally Posted by Slick Fork

Now, just to be sure when he says "Morton's Iodized Salt" he's talking about an American Brand name for table salt correct???

Yep.

Originally Posted by Slick Fork

So, with all that done do you guys think I could be confident trusting the reading I'll take after supper?

I think you should be fine. Please post the measurement you get with both devices now that you've calibrated, it sounds like they'll be pretty close.