Swing Arm Hydrometer Warning! - Aquarium Advice

Pghjeff71 · 06-04-2005, 05:03 PM

Ever since I've been in this hobby I've always used a swing arm hydrometer of one type or the other. I've been using the "Deep Six" model for the last several months and while being here on the AA forums have read nothing but bad things about these. I've always thought, "well how bad can these things truly be". Well after a disease outbreak and needing to use hyposalinity for a quarantine tank I decided to purchase a refractometer. The difference between the two devices is staggering.

- The swing arm hydrometer is off by a whopping -.5/[acronym:1a77b0b341="Specific gravity"]SG[/acronym:1a77b0b341]; for example the refractometer showed my main tank at 1.26SG while the hydrometer showed 1.21SG.

Let this be a warning to everyone in this hobby. Spend the $45 dollars and get a refractometer today! It's the single best tool you can buy if you are serious about the care of your tanks.

Pghjeff71 · 06-04-2005, 05:09 PM

Oh as a sidenote, while I was typing this article I remembered I also have a glass hydrometer (the kind you drop in the water and see where it floats). I've had this thing probably for a good five years now, and this one is +.2SG as compared to the refractometer:

Main Tank:

1.23SG (refractometer)
1.25SG (glass hydrometer)
1.18SG (swing arm hydrometer)

Not as bad as the swing arm hydrometer, but still leaves room for doubt.

- Jeff

Scatcat · 06-04-2005, 05:11 PM

Thank you for sharing, this is one of the reasons why I read these post everyday. I use a refractometer and I'm glad I spent the money. As much as I stress about my tank I want to make sure all readings are accurate.

Kam · 06-04-2005, 06:49 PM

I also just recently changed from a hydrometer to a refractometer. I had similar results, a .5 difference between the two. My refractometer readings match that of the [acronym:a6381297b6="Local Fish Store"]LFS[/acronym:a6381297b6] that uses some kind of digital meter.

Jermz79 · 06-04-2005, 07:04 PM

Same here ... I was using an "Instant Ocean" hydrometer and it was giving me a reading of 1.028 ... I decided to go ahead and get myself a refractometer (the blue one from premiumaquatics.com) and when I got it my readings were 1.024!

A BIG DIFFERENCE!!!!

Needless to say the hydrometer went in the garage!!!

Phyl · 06-04-2005, 07:55 PM

That's so funny. I've noticed exactly the opposite. Most of my fellow reefers that think they have their tanks running at 1.025 using a swing arm actually have their water at 1.029 using the refractometer. Wrong in any direction is just wrong, but I find it interesting that it is wrong in both directions.

revhtree · 06-04-2005, 08:09 PM

My Refrac says 1.025 my Instant ocean Hydro says 1.025..

dianeww · 06-04-2005, 08:17 PM

I'm going with you, revtree....lots of conflicting advice here. If I stick with my floating arm hydrometer and just keep the level consistent (mine reads 1.023, and that's what I adjust the new water to too), that can't be too far off the mark.

dianeww · 06-04-2005, 08:18 PM

Sorry about the misspelling, revhtree!

Phyl · 06-04-2005, 09:46 PM

As the salt deposits over time they will become increasingly inaccurate. I'd double check it every month at the [acronym:7f2937421b="Local Fish Store"]LFS[/acronym:7f2937421b], just to be sure it hasn't changed any.

06-04-2005, 05:03 PM	#1
Pghjeff71 Aquarium Advice Regular Join Date: Mar 2005 Location: Pittsburgh PA Posts: 64 Images: 3	Swing Arm Hydrometer Warning! Ever since I've been in this hobby I've always used a swing arm hydrometer of one type or the other. I've been using the "Deep Six" model for the last several months and while being here on the AA forums have read nothing but bad things about these. I've always thought, "well how bad can these things truly be". Well after a disease outbreak and needing to use hyposalinity for a quarantine tank I decided to purchase a refractometer. The difference between the two devices is staggering. - The swing arm hydrometer is off by a whopping -.5/[acronym:1a77b0b341="Specific gravity"]SG[/acronym:1a77b0b341]; for example the refractometer showed my main tank at 1.26SG while the hydrometer showed 1.21SG. Let this be a warning to everyone in this hobby. Spend the $45 dollars and get a refractometer today! It's the single best tool you can buy if you are serious about the care of your tanks.

06-04-2005, 05:11 PM	#3
Scatcat Aquarium Advice Freak Join Date: Apr 2005 Location: TX USA Posts: 347	Thank you for sharing, this is one of the reasons why I read these post everyday. I use a refractometer and I'm glad I spent the money. As much as I stress about my tank I want to make sure all readings are accurate. __________________ -Scatcat- Don't take life too seriously, No one gets out alive.

06-04-2005, 06:49 PM	#4
Kam Aquarium Advice Activist Join Date: May 2005 Location: Grand Island, NY Posts: 137	I also just recently changed from a hydrometer to a refractometer. I had similar results, a .5 difference between the two. My refractometer readings match that of the [acronym:a6381297b6="Local Fish Store"]LFS[/acronym:a6381297b6] that uses some kind of digital meter. __________________ 55 Gal [acronym:d952257e2c="Fish only with live rock"]FOWLR[/acronym:d952257e2c] 105 lbs Live rock from [acronym:d952257e2c="Live rock"]LR[/acronym:d952257e2c].com 2 Yellow Tail Damsels 2 Green Chromis 1 Emerald Crab 3 Peppermint Shrimp 4 Scarlet Hermit Crabs 1 Blue Knuckle Hermit Crab 1 Large Turbo Snail Hitchhickers: 3 Purple sea urchins, lots of rock crabs, pistol shrimp, brittle stars, snails, worms, etc. and aiptasia, aiptasia, aiptasia (it was free $$)

06-04-2005, 07:04 PM	#5
Jermz79 Aquarium Advice Addict Join Date: Apr 2005 Location: Spring Hill, FL Posts: 1,157	Same here ... I was using an "Instant Ocean" hydrometer and it was giving me a reading of 1.028 ... I decided to go ahead and get myself a refractometer (the blue one from premiumaquatics.com) and when I got it my readings were 1.024! A BIG DIFFERENCE!!!! Needless to say the hydrometer went in the garage!!! __________________ God grant me the serenity to accept the thing's I can not change, the courage to change the thing's I can and the wisdom to know the difference! R.I.P Walena K. Cox 7/7/62 - 8/11/2002

06-04-2005, 07:55 PM	#6
Phyl Aquarium Advice Addict Moderator Emeritus Join Date: Oct 2004 Location: NJ Posts: 2,107 Images: 30	That's so funny. I've noticed exactly the opposite. Most of my fellow reefers that think they have their tanks running at 1.025 using a swing arm actually have their water at 1.029 using the refractometer. Wrong in any direction is just wrong, but I find it interesting that it is wrong in both directions. __________________ Phyllis Join the NJ Reef Club Today! Saving the world's reefs one living room at a time! Next meeting: Eric Borneman, Dana Riddle, & Charles Mazel on October 25, 2008

06-04-2005, 05:09 PM	#2
Pghjeff71 Aquarium Advice Regular Join Date: Mar 2005 Location: Pittsburgh PA Posts: 64 Images: 3	Oh as a sidenote, while I was typing this article I remembered I also have a glass hydrometer (the kind you drop in the water and see where it floats). I've had this thing probably for a good five years now, and this one is +.2SG as compared to the refractometer: Main Tank: 1.23SG (refractometer) 1.25SG (glass hydrometer) 1.18SG (swing arm hydrometer) Not as bad as the swing arm hydrometer, but still leaves room for doubt. - Jeff

06-04-2005, 08:09 PM	#7
revhtree Aquarium Advice Addict Community Admin Moderator Emeritus Join Date: Apr 2004 Location: Rossville. Ga Posts: 4,047 Images: 1	My Refrac says 1.025 my Instant ocean Hydro says 1.025.. __________________ Remember to Keep Christ First! 120G - Deltec AP601 Skimmer - Reefkeeper2 - Geo 618 - (2)Tunze 6100 - Tunze 6212 Wave Box - (2) 250w MH's w/VHO

06-04-2005, 08:17 PM	#8
dianeww Aquarium Advice Freak Join Date: Apr 2005 Location: rockport, massachusetts Posts: 486	I'm going with you, revtree....lots of conflicting advice here. If I stick with my floating arm hydrometer and just keep the level consistent (mine reads 1.023, and that's what I adjust the new water to too), that can't be too far off the mark.

06-04-2005, 08:18 PM	#9
dianeww Aquarium Advice Freak Join Date: Apr 2005 Location: rockport, massachusetts Posts: 486	Sorry about the misspelling, revhtree!

06-04-2005, 09:46 PM	#10
Phyl Aquarium Advice Addict Moderator Emeritus Join Date: Oct 2004 Location: NJ Posts: 2,107 Images: 30	As the salt deposits over time they will become increasingly inaccurate. I'd double check it every month at the [acronym:7f2937421b="Local Fish Store"]LFS[/acronym:7f2937421b], just to be sure it hasn't changed any. __________________ Phyllis Join the NJ Reef Club Today! Saving the world's reefs one living room at a time! Next meeting: Eric Borneman, Dana Riddle, & Charles Mazel on October 25, 2008

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