Kessil

Do we REALLY need a refractometer?

A_Lee

A_Lee

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Well, we all know the answer to this is "it is highly recommended," if not a "necessity." But I figure I needed a post title that would grab some of yours' attention :)

SO
My buddy was thinking about swooping up a JBJ refractometer ... anyone have one, or used one, or have any thoughts on this?
 
Refractometers (once calibrated!) are just nice and quick. A few drops on the lens, then look through. Even if it's not calibrated, you can still check your tanks water and your water change water to make sure that the reading is the same.

Floating hydrometers may be more accurate but a huge PITA to use.

The hydrometers with the swinging arms are pretty easy to use, but sometimes they stick and are hard to use...plus I think they are more temperature dependant than refractometers.

So no, you don't need one, but if you have one, you'll be glad you have it!

One nice thing about a swinging-arm hydromter (lke the deep-six) is that you can sort of hang it in your water change bucket and adjust your salt while it constantly reads the salinity.

V
 
[quote author=Vincerama2 link=topic=6102.msg77434#msg77434 date=1233256173]
Refractometers (once calibrated!) are just nice and quick. A few drops on the lens, then look through. Even if it's not calibrated, you can still check your tanks water and your water change water to make sure that the reading is the same.

Floating hydrometers may be more accurate but a huge PITA to use.

The hydrometers with the swinging arms are pretty easy to use, but sometimes they stick and are hard to use...plus I think they are more temperature dependant than refractometers.

So no, you don't need one, but if you have one, you'll be glad you have it!

One nice thing about a swinging-arm hydromter (lke the deep-six) is that you can sort of hang it in your water change bucket and adjust your salt while it constantly reads the salinity.

V

[/quote]

Haha, thanks Vince -but I already have a refractometer :) The title was only to grab peoples attention ;)
What I really wanted to know was any feedback anyone might have regarding JBJ refractometers.
 
Can't speak to the JBJ one. I have used the simple Marine Depot one for years and been very pleased with it. Check it on occasion with the salinity standard but have never needed to adjust it.
 
[quote author=badbread link=topic=6102.msg77439#msg77439 date=1233257047]
I have the marinedepot one, best $40 I've spent so far.
[/quote]
+1
 
A properly calibrated refractometer, with a known salinity solution near the point you're trying to measure and NOT RO/DI water, should remove any issues with brand name being "off"
 
[quote author=Gomer link=topic=6102.msg77512#msg77512 date=1233291977]
technically, conductivity is not proportional to index of refraction. use at your own risk :)
[/quote]

Fortunately, I don't care about the refractive index of my tank's water, but rather its salinity. Which of course is defined in terms of conductivity relative to a reference solution. :)
 
Without this turning into a big ol chemistry hoopla, I'll just say sorta. ..ok. I can't leave it at that lol. Salinity is dissolved salt content independent of salt identity. Conductivity is due to ion transport in water, but the conductivity is dependent on the identity of the ion. Different ions have different conductivity. So...you can have two identical conductivities result from different salinities made up of different ionic composition. I'm not sure what the perturbation of say..a 10% random walk in ion concentrations will do to the salinity perturbation of "salt water", but it might be a fun ultra geeky thing to do on the weekend lol. ...so it might be good enough, or it might have some significant flaws if you for example use Epsom salt vs MgCl2 for Mg dosing (since the conductivity of (SO4)2- is low compared to Cl-).
 
Ah, but salinity is no longer defined as total dissolved material independent of identity (at least in the oceanographic community) since that's impossible to measure directly. In 1978 it was re-defined to be the ratio of conductivity of the sample relative to the conductivity of 32.4356 grams of KCl dissolved in 1.0 kg H2O.

http://oceanworld.tamu.edu/resources/ocng_textbook/chapter06/chapter06_01.htm

:D
 
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hello?
oh crap I lost count!
 
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