hydrometer or refractonator

sassyfrassy · 11/06/2009, 10:41 AM

I broke my nice floating hydrometer and must buy another one. I still have a couple of plastic ones, but don't know how accurate they are. What is a refractionator - pricy - do I need one? Also what SG is best while I cycle?

shereth · 11/06/2009, 10:50 AM

A properly calibrated refractometer is much more accurate than a hydrometer. I've heard of people having an SG off by as much as .03 due to bad hydrometers and depending on what you stock in your tank, a variance of that much can prove to be problematic or even fatal. A $50 refractometer is a lot cheaper than $1000+ worth of sensitive livestock

der_wille_zur_macht · 11/06/2009, 10:52 AM

When in doubt, follow natural seawater properties. For sg, that means around 1.025.

As far as how you measure that, most people will shout that you should throw away all your hydrometers and buy a refractometer. IMHO, it doesn't really matter which tool you use, as long as you follow these guidelines:

1) Make sure it's calibrated. Both hydrometers and refractometers can be off.

2) Make sure you're using it correctly. Again, it's totally possible to misuse either.

Hydrometers get a bad rep in this hobby, and while it's true that they can give bad readings, 99% of the time it's because people ignore the above two guidelines. And ignoring these guidelines with a refractometer can lead to bad data, too.

sassyfrassy · 11/06/2009, 11:00 AM

I had a nice floating glass hydrometer (about 1'tall - larger bulb at bottom, slender tube above) that I knew was accurate (tested by LFS), but I can't seem to find another one like it. Do you know which one I'm talking about or where to get one?

jenglish · 11/06/2009, 11:03 AM

floating hydrometeres can be pretty accurate, the swing arm hydrometers are not very accurate though they are generally stable. If you keep it clean and knock all the bubbles off the needle, and know it is over by .003... it will always be off by the same amount. Honestly though it is so much easier to get a hydrometer off ebay for 25 bucks than mess with a swing arm.

der_wille_zur_macht · 11/06/2009, 11:05 AM

Check homebrew places if no marine aquarium sources have it. That style is common for beer making. I have one but only use it for that purpose since it's so fragile.

Randy Holmes-Farley · 11/06/2009, 11:18 AM

Tropic Marin makes (or at least made) good floating glass hydrometers that were quite accurate.

Conductivity meters are also highly accurate, and can be used for other things (like limewater potency), but refractometers can be very accurate too.

If you get a refractometer, be sure to calibrate it with a seawater standard, not RO/DI water or a salt standard that came with it.

These have more:

Refractometers and Salinity Measurement
http://reefkeeping.com/issues/2006-12/rhf/index.php

Temperature Corrections for Hydrometers
http://reefkeeping.com/issues/2004-07/rhf/index.htm

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

Specific Gravity Measurement
http://www.advancedaquarist.com/2002/1/chemistry

Using Conductivity to Measure Salinity
http://web.archive.org/web/200406040....aspx?aid=1804

sassyfrassy · 11/06/2009, 11:40 AM

Thanks for the references!

11/06/2009, 10:41 AM	#1
sassyfrassy Registered Member Join Date: Jun 2009 Location: Kings Mountain, NC Posts: 912	hydrometer or refractonator I broke my nice floating hydrometer and must buy another one. I still have a couple of plastic ones, but don't know how accurate they are. What is a refractionator - pricy - do I need one? Also what SG is best while I cycle? __________________ Faith, hope, and love abide; but the greatest of these is love. Current Tank Info: 40g breeder DT LR & Macro Algae - 2" sand, 6 T5s & 2 fans in hood; 30gL sump/fuge w/MSX 200 skimmer & other equip.; (mangroves in DT - roots are great look)

11/06/2009, 10:50 AM	#2
shereth Registered Member Join Date: Oct 2009 Location: Laveen, AZ Posts: 73	A properly calibrated refractometer is much more accurate than a hydrometer. I've heard of people having an SG off by as much as .03 due to bad hydrometers and depending on what you stock in your tank, a variance of that much can prove to be problematic or even fatal. A $50 refractometer is a lot cheaper than $1000+ worth of sensitive livestock Last edited by shereth; 11/06/2009 at 10:50 AM. Reason: misspelling

11/06/2009, 10:52 AM	#3
der_wille_zur_macht Team RC Member Join Date: Sep 2003 Location: NY Posts: 17,749	When in doubt, follow natural seawater properties. For sg, that means around 1.025. As far as how you measure that, most people will shout that you should throw away all your hydrometers and buy a refractometer. IMHO, it doesn't really matter which tool you use, as long as you follow these guidelines: 1) Make sure it's calibrated. Both hydrometers and refractometers can be off. 2) Make sure you're using it correctly. Again, it's totally possible to misuse either. Hydrometers get a bad rep in this hobby, and while it's true that they can give bad readings, 99% of the time it's because people ignore the above two guidelines. And ignoring these guidelines with a refractometer can lead to bad data, too. __________________ Inconveniencing marine life since 1992 "It is my personal belief that reef aquaria should be thriving communities of biodiversity, representative of their wild counterparts, and not merely collections of pretty specimens growing on tidy clean rock shelves covered in purple coralline algae." (Eric Borneman)

11/06/2009, 11:00 AM	#4
sassyfrassy Registered Member Join Date: Jun 2009 Location: Kings Mountain, NC Posts: 912	I had a nice floating glass hydrometer (about 1'tall - larger bulb at bottom, slender tube above) that I knew was accurate (tested by LFS), but I can't seem to find another one like it. Do you know which one I'm talking about or where to get one? __________________ Faith, hope, and love abide; but the greatest of these is love. Current Tank Info: 40g breeder DT LR & Macro Algae - 2" sand, 6 T5s & 2 fans in hood; 30gL sump/fuge w/MSX 200 skimmer & other equip.; (mangroves in DT - roots are great look)

11/06/2009, 11:03 AM	#5
jenglish Marquis de Carabas Join Date: Aug 2008 Location: Evansville, IN Posts: 2,523	floating hydrometeres can be pretty accurate, the swing arm hydrometers are not very accurate though they are generally stable. If you keep it clean and knock all the bubbles off the needle, and know it is over by .003... it will always be off by the same amount. Honestly though it is so much easier to get a hydrometer off ebay for 25 bucks than mess with a swing arm. __________________ Jeremy Brown liquor never hurt anybody “Je n'ai pas besoin de cette hypothèse" Pierre-Simon Laplace I should want to cook him a simple meal, but I shouldn't want to cut into him, to tear the flesh, to wear the flesh, to be born unto new worlds where his flesh becomes my key. Current Tank Info: broken and dry

11/06/2009, 11:05 AM	#6
der_wille_zur_macht Team RC Member Join Date: Sep 2003 Location: NY Posts: 17,749	Check homebrew places if no marine aquarium sources have it. That style is common for beer making. I have one but only use it for that purpose since it's so fragile. __________________ Inconveniencing marine life since 1992 "It is my personal belief that reef aquaria should be thriving communities of biodiversity, representative of their wild counterparts, and not merely collections of pretty specimens growing on tidy clean rock shelves covered in purple coralline algae." (Eric Borneman)

11/06/2009, 11:18 AM	#7
Randy Holmes-Farley Reef Chemist Join Date: Apr 2001 Location: Arlington, Massachusetts Posts: 86,233	Tropic Marin makes (or at least made) good floating glass hydrometers that were quite accurate. Conductivity meters are also highly accurate, and can be used for other things (like limewater potency), but refractometers can be very accurate too. If you get a refractometer, be sure to calibrate it with a seawater standard, not RO/DI water or a salt standard that came with it. These have more: Refractometers and Salinity Measurement http://reefkeeping.com/issues/2006-12/rhf/index.php Temperature Corrections for Hydrometers http://reefkeeping.com/issues/2004-07/rhf/index.htm Reef Aquarium Salinity: Homemade Calibration Standards http://reefkeeping.com/issues/2004-06/rhf/index.htm Specific Gravity Measurement http://www.advancedaquarist.com/2002/1/chemistry Using Conductivity to Measure Salinity http://web.archive.org/web/200406040....aspx?aid=1804 __________________ Randy Holmes-Farley Current Tank Info: 120 mixed reef

11/06/2009, 11:40 AM	#8
sassyfrassy Registered Member Join Date: Jun 2009 Location: Kings Mountain, NC Posts: 912	Thanks for the references! __________________ Faith, hope, and love abide; but the greatest of these is love. Current Tank Info: 40g breeder DT LR & Macro Algae - 2" sand, 6 T5s & 2 fans in hood; 30gL sump/fuge w/MSX 200 skimmer & other equip.; (mangroves in DT - roots are great look)