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

Slick Fork · #1 05-29-2007, 06:21 PM

Hi there,

Just got a new refractometer in the mail today and wow was my hydrometer ever out. My Hydrometer was telling me I was at 1.024 and the new refractometer says 1.030. 6 POINTS OUT!!! I expected to see a difference but that's huge.

So anyways, I wanted to bring my salinity back down to 1.024 and my plan is really simple. I don't want to do it all at once of course but I figure if I pull a couple of litres of SW out every day and top back up with fresh RO water that should be slow enough do you think? The system is a 100gal display with ~40 gallons in the sump.

Is my plan to aggresive, or to conservative? Should I maybe just do my adjusting during water changes? Let me know what you think.

Cheers

Zylumn · #2 05-29-2007, 06:28 PM

Same thing with me when I got my refractometer I was blown away at how many ppl my hydrometer was off. As I said before my hydrometer worked fine but they just glued the numbers in the wrong spots.

wickedfrags · #3 05-29-2007, 06:40 PM

Sounds like a reasonable plan. I would think 2-3 litres a day will do the job until you get it down to where you want it. Some people (inluding myself) maintain their salinity at 1.026 so you do not have to drop it down that much if you don't want to.

Quote:

Originally Posted by Slick Fork

Hi there,

Just got a new refractometer in the mail today and wow was my hydrometer ever out. My Hydrometer was telling me I was at 1.024 and the new refractometer says 1.030. 6 POINTS OUT!!! I expected to see a difference but that's huge.

So anyways, I wanted to bring my salinity back down to 1.024 and my plan is really simple. I don't want to do it all at once of course but I figure if I pull a couple of litres of SW out every day and top back up with fresh RO water that should be slow enough do you think? The system is a 100gal display with ~40 gallons in the sump.

Is my plan to aggresive, or to conservative? Should I maybe just do my adjusting during water changes? Let me know what you think.

Cheers

Reefer Rob · #4 05-29-2007, 07:10 PM

Double check your refractometer with Pinpoint 53.0 uS calibrating fluid. Many of the refractometers that find their way into the aquarium trade are for testing brine not sea water, and will give you an inaccurate salinity reading

Slick Fork · #5 05-29-2007, 08:15 PM

I ordered it from J&L so I would hope that it's one meant for the aquarium trade! I did calibrate it with the "ultra pure" water that came with it. Is that alright or should I locate some of this pinpoint 53 stuff?

Okguy · #6 05-29-2007, 08:55 PM

I would confirm the refractometer readings first before making changes. Take a water sample to you're local store (if there is one around) and have them confirm the readings. If the livestock doesn't appear to be stressed with your current water parameters, you might as well take your time and make sure the changes are required.

I once made slight changes because a new thermometer I bought was faulty and the consequences were pretty severe. Just better to be safe than sorry.

Slick Fork · #7 05-29-2007, 09:04 PM

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 · #8 05-29-2007, 09:19 PM

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 · #9 05-29-2007, 10:06 PM

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 · #10 05-30-2007, 01:16 AM

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.