Swing Arm Hydrometer Vs. Refractometer Vs. Floating Hydrometer

[steelhealr]

My pet peeve.....be careful...salinity and s.g. are NOT THE SAME PARAMETERS and these terms should not be used interchangeably. We work very hard at keeping our marine tanks......know your terms. SH

 

[Musho3210]

specific gravity, its about density i think

salinity, its about dissolved salts


They work together but arent the same.

 

[andywg]

As someone has frankenposted here:

Floating Hydrometers (I shall ignore swing arms) are almost certainly just as accurate at our level as refractometers, you just have to remember that SG is affected by temperature. Reef Fishes Volume 1 has a great table showing you how to adjust your readings from a hydro at what temperature. I think that this is the biggest source of "inaccuracies"; people reading the temp off a 28/29 degree tank with a hydro designed for 25, or even 20 degrees. The error is (IMO) in the use, not the instrument.

Also, remember most of the refractometers we can afford do not run the whole scale very well. If you calibrate them at 0 (with RO) then there is a good chance that 35 ppt salinity will not actually be 35. If using a refractometer you are better off creating a known salinity solution and calibrating to that.

I think the most important thing is to know your tool, how it is calibrated and how to read it. When mixing salt you can leave a floating hydrometer in the mixing bucket which is a lot easier than continually taking readings.

 

[steelhealr]

As andywg said....floating hydrometers are good...if you don't mind squinting at a floating tube while your Maxijets are going. A refractometer is still so much more fun to use. SH

 

[andywg]

As andywg said....floating hydrometers are good...if you don't mind squinting at a floating tube while your Maxijets are going. A refractometer is still so much more fun to use. SH

As I consider myself a fairly serious aquarist, you will never find maxijets anywhere near my tanks However refractometers are much fun to use.

 

[snowclown]

andywg,
Could you explain to us all why you choose to ignore the floating swing arms ??

I have used them from the early seventies, to the present day, with no deviations from any other calobrated tests! vettenary or otherwise.

 

[Musho3210]

not just him, but many others hate them. How would you know that they are accurate if you arent using a controlled experiment snowclown?

 

[andywg]

Swing arm are too easy to give an "off" result. All it takes is one bubble near the arm and readings can be thrown off. Floating hydrometers are less likely to give an "off" result (but can still be misread - which is pretty hard on a refractometer)

 

[Musho3210]

i mis-read my refractometer all the time... numbers are too close together, but i still love it, even if the hinges that swivel my cover on my prism have rusted and every time i turn it it seems like it is so close to breaking.

 

[k.o.d]

Have used all the above methods and have found the refractometer to be by far the best, easiest and most consistent.

if you have several hundred pounds worth of stock this should really be seen as an investment.

Steve

 

[Adrinal]

Swing arm, absolutly. BUT with refracto back up.

You can either purchace a refracto or use the one from a friend or store.



1)Get some water mixed to where you want it using a refracto
2)put that water in your swing arm.
3)Mark that level with a scratch and perminate marker (use a ruler for the scratch because you will use this till it drops and breaks, so make it look nice... gonna happen you know it! lol).
4)Rinse habbitually


If you like, take your swing arm(s) in for a check up once and a while.

PS I have a couple of swing arms and the FS refracto too.

 

[Musho3210]

swing arms and refract combinations are great, especially when mixing saltwater.