Refractometer or Hydrometer

[alicel]

If you can't get this, you can also try one of those mini glass hydrometers off of Amazon. I have both the Tropic Marin and Amazon cheapo version, and I've found that the ripoff tracks fairly closely with the Tropic Marin model.

Also: did you ensure that the refractometer was for salinity and not alcohol? I bought (and used) the one meant for alcohol.

I didn't check for that but I will look as soon as I get home!

 

[alicel]

I killed my tank by trusting a swing arm hydrometer a long time ago. A temperature compensated hydrometer or a refractometer & calibration solution is all I'd ever use.

That's a fear of mine!

 

[alicel]

Thank you all for your help! I am grateful for your responses! I'm going to look into what kind of refractometer I have (I didn't know there were different ones for salt/alcohol) and I'm going to look into a calibration fluid.
Again, THANK YOU!

 

[Vette67]

If you look, that refractometer is for brewing beer (I have one for brewing beer like that). So I would believe the hydrometer before I'd believe that refractometer. You need a saltwater refractometer, not a brewing refractometer. Wort, is unfermented beer. It is the sugary water that you get when you brew the grains. The yeast then ferments the sugar in the wort into alcohol and carbon dioxide. There's a formula to compare the beginning specific gravity of your wort to the ending speciifc gravity, to calculate the alcohol content (alcohol has a specific gravity lower than water, lower than 1.0).

Anyhow, that's more information about beer brewing than you probably wanted to know. But that explains why I wouldn't believe that refractometer. It's calibrated for much higher specific gravity than your tank will ever encounter.

 

[alicel]

If you look, that refractometer is for brewing beer (I have one for brewing beer like that). So I would believe the hydrometer before I'd believe that refractometer. You need a saltwater refractometer, not a brewing refractometer. Wort, is unfermented beer. It is the sugary water that you get when you brew the grains. The yeast then ferments the sugar in the wort into alcohol and carbon dioxide. There's a formula to compare the beginning specific gravity of your wort to the ending speciifc gravity, to calculate the alcohol content (alcohol has a specific gravity lower than water, lower than 1.0).

Anyhow, that's more information about beer brewing than you probably wanted to know. But that explains why I wouldn't believe that refractometer. It's calibrated for much higher specific gravity than your tank will ever encounter.

I ordered it from Amazon. I wasn't aware that there is a difference. I just checked my order and I did, in fact, order the one for brewing. I am going to return it today and order the correct one!
Rookie mistake

 

[davidcalgary29]

I ordered it from Amazon. I wasn't aware that there is a difference. I just checked my order and I did, in fact, order the one for brewing. I am going to return it today and order the correct one!
Rookie mistake

No, it's not. You can see everyone who've been caught by this in the comments -- they're the ones who have given all the one-star reviews. Seriously, Amazon and the seller really do need to clearly indicate the intended use of these things.

I couldn't find the source of my problems until Jay Hemdal told me that -- ahem -- I had probably bought, and used, a beerfractometer. Apparently there are even some for blood!

 

[alicel]

No, it's not. You can see everyone who've been caught by this in the comments -- they're the ones who have given all the one-star reviews. Seriously, Amazon and the seller really do need to clearly indicate the intended use of these things.

I couldn't find the source of my problems until Jay Hemdal told me that -- ahem -- I had probably bought, and used, a beerfractometer. Apparently there are even some for blood!

Who knew!!
There is always something to be learned in this hobby.

 

[Randy Holmes-Farley]

I ordered it from Amazon. I wasn't aware that there is a difference. I just checked my order and I did, in fact, order the one for brewing. I am going to return it today and order the correct one!
Rookie mistake

There is. That's a BRIX refractometer. Could work, but likely is not the right range or precision.


Refractometers And Salinity Measurement

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Brix Refractometers

A commonly manufactured type of refractometer is called a Brix refractometer. Its scale usually reads in Brix, or % Brix (percent Brix). These refractometers are used in many industries to measure the concentration of sugar in water such as in the soft drink industry. They can be used to measure seawater’s salinity, but are not always precise enough around the range of seawater’s refractive index to be useful. A resolution of 0.2% Brix is common, and that is borderline acceptable for the reasons detailed below.

Table 4 shows the relationship between seawater salinity, refractive index and % Brix. If a refractometer has a resolution (not accuracy, but resolution, which is the finest amount it can distinguish) of 0.2 % Brix, then that translates to about +/- 1 ppt. So the best resolution would translate to 35 ppt seawater reading 34-36 ppt, which may be adequate for reef aquarists. A Brix refractometer that reads 0 to 10 % Brix with a resolution of 0.1% Brix might be a fine choice for determining seawater salinity in a reef aquarium, (although they are not inexpensive). Some Brix refractometers have a resolution of 0.5 % Brix or even 1% Brix, and they would not be suitable choices.

 

[davidcalgary29]

There is. That's a BRIX refractometer. Could work, but likely is not the right range or precision.


Refractometers And Salinity Measurement

Refractometers and Salinity Measurement - REEFEDITION

Title photo by R2R member Rskillz By Randy Holmes-Farley Salinity is one of the most important parameters measured in reef aquaria. It controls not only the salt balance between an organism and its surrounding environment, but also the levels of a host of ions Read more here...

www.reefedition.com

Brix Refractometers

A commonly manufactured type of refractometer is called a Brix refractometer. Its scale usually reads in Brix, or % Brix (percent Brix). These refractometers are used in many industries to measure the concentration of sugar in water such as in the soft drink industry. They can be used to measure seawater’s salinity, but are not always precise enough around the range of seawater’s refractive index to be useful. A resolution of 0.2% Brix is common, and that is borderline acceptable for the reasons detailed below.

Table 4 shows the relationship between seawater salinity, refractive index and % Brix. If a refractometer has a resolution (not accuracy, but resolution, which is the finest amount it can distinguish) of 0.2 % Brix, then that translates to about +/- 1 ppt. So the best resolution would translate to 35 ppt seawater reading 34-36 ppt, which may be adequate for reef aquarists. A Brix refractometer that reads 0 to 10 % Brix with a resolution of 0.1% Brix might be a fine choice for determining seawater salinity in a reef aquarium, (although they are not inexpensive). Some Brix refractometers have a resolution of 0.5 % Brix or even 1% Brix, and they would not be suitable choices.

Great summary! My beerfractometer gave me erroneous readings of 10ppt lower than actual salinity, so I unknowingly (or negligently) made my water hypersaline to compensate before I discovered The Evil Truth About Amazon Refractometers. I recalibrated with saline solution, and keep it around for emergencies, but certainly don't use it on a day-to-day basis.

 

[stanleo]

To your question of which to trust, a refractometer every time. But one that is designed for salt water tanks. Years ago when I took over a tank the only thing I had was a hydrometer. It read 1.024 every time both in the tank and the new water for water changes. Fish seemed fine but I couldn't keep inverts alive for very long. One day, I got a shipment from an online vender that accidently sent me a sea hare. I drip acclimated it and for a week it stayed in the top back corner and wouldn't budge. I got curious and took a water sample to a LFS and they checked my salinity with their refractometer and my salinity was well over 1.035. If fact I think I remember it being 1.040. I bought a refractometer right then and there and tossed the hydrometer as soon as I got home. Fish can handle varying STABLE levels of saltwater but inverts cannot.

 

[Randy Holmes-Farley]

So my question is this - which device do you trust over the other: refractometer or hydrometer?

Both hydrometers and refractometers can work well, in general, but for those who do not yet have any device, don't fall for this dichotomy. Pick a better option: a conductivity meter.

 

[ReefGeezer]

Both hydrometers and refractometers can work well, in general, but for those who do not yet have any device, don't fall for this dichotomy. Pick a better option: a conductivity meter.

FWIW, & since my post implied the aforementioned dichotomy, I agree with Randy. I use a refractometer. When it comes time to replace it, I'll choose a conductivity meter. It's fast, simple, accurate.

 

[blasterman]

I still use a Instant Ocean plastic needle hydro.

Its significantly quicker than a refractometer to use and doesn't require calibration. Can also survive a drop on cement floor. My last refractometer didn't. I know a lot of you are into testing and not into reefkeeping though. You love to test and calibrate things.

I've calibrated it vs two refractometers and its within a point of accuracy. Its also consistent . U need to tap it a few times to knock off air bubbles ....then its spot on.

When I finally drop it for the nth time and shatter it I might buy another. As long as my water is within a point or so in either direction I dont care.

I should point out that all the salinity errors I see in this forum occur with refractometers. Typically calibration issues. Oh wait...I dont have to calibrate a piece of floating plastic. Just tap the air bubbles off.

 

[KStatefan]

Both hydrometers and refractometers can work well, in general, but for those who do not yet have any device, don't fall for this dichotomy. Pick a better option: a conductivity meter.

I know you recommend the Orion model 128 if you can find one on Ebay what about their newer models or another brand like Oakton?

 

[Randy Holmes-Farley]

I know you recommend the Orion model 128 if you can find one on Ebay what about their newer models or another brand like Oakton?

Other brands and models can all be good choices.

I like the one I use because it uses a 4 electrode probe (reduces some types of interferences and errors), allows a very wide range from RO/DI to limewater/kalwkasser to seawater, and is fast to come to temperature compensation (faster than the Pinpoint I also used).

 

[zukihara]

That Hanna salinity meter is pretty darn sweet.

 

[alicel]

I still use a Instant Ocean plastic needle hydro.

Its significantly quicker than a refractometer to use and doesn't require calibration. Can also survive a drop on cement floor. My last refractometer didn't. I know a lot of you are into testing and not into reefkeeping though. You love to test and calibrate things.

I've calibrated it vs two refractometers and its within a point of accuracy. Its also consistent . U need to tap it a few times to knock off air bubbles ....then its spot on.

When I finally drop it for the nth time and shatter it I might buy another. As long as my water is within a point or so in either direction I dont care.

I should point out that all the salinity errors I see in this forum occur with refractometers. Typically calibration issues. Oh wait...I dont have to calibrate a piece of floating plastic. Just tap the air bubbles off.

I did end up buying a refractometer and that's what I've been using since I first made this post. However, I have used the needle hydrometer sine then to compare it to the validity of the refractometer and to my surprise it has been spot on.
I do prefer the refractometer and always have since even before getting my own tank. But at least now I know that if I break one the other will get me along just fine.

 

[Randy Holmes-Farley]

FWIW, I tested two swing arms years ago. Mixed results. The temp correction worked well even if they were inaccurate. lol

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated!

This month, Randy explains and reviews specific gravity.

reefs.com

So how do these hydrometers measure up? In my tank the water was measured to be S=35 ± 0.5 by conductivity. Using the Deep Six swing arm hydrometer I got readings of S=32.5 ± 0.5 at 81 °F and S=32 ± 0.5 at 68 °F. Using the SeaTest I got S=34.5 ± 0.5 at 81 °F and S=34 ± 0.5 at 68 °F.