Refractometer vs Tropic Marin Hydrometer

[schrodi]

I will soon have a FOWLR tank and I'm trying to decide on which way to go - to measure the salinity of my tank and and saltwater that I make up. Anyone have both? What do you think?

I'm sure the refractometer is very accurate. How difficult is it to use and maintain? Sure is expensive. Wonder if it would be my best choice? I see one model advertized at premium aquatics for $114.95. Another one advertized on I believe marine depot for $85. Wonder if they are the same - or is one better?

Tropic Marin Hydrometer is supposed to be calibrated at 77 degrees. Shouldn't have to correct much for temp. Much cheaper. I see one at premium aquatics for $19.95.

Which should I go with? Anyone have both? Don't mind spending money if I need to - but don't need to just waste money either. Comments?

thanks,
keith in ohio

[npaden]

The Tropic Marin hydrometers are very difficult to use IMO. You have to have a deep spot (12" at least) of perfectly calm water to allow them to float and then are somewhat difficult to read. As far as I know they are accurate though except you would be suprised at how just a slight temperature difference of 2 degrees will affect your specific gravity. Our reef club tested one against a refractometer and it was .0005 difference in specific gravity. (1.025 vs. 1.0245 or something like that).
The refractometers are VERY easy to use once they are calibrated. Takes about 15 seconds. VERY accurate. I use the swing arm cheap plastic hydrometers but I check them against a friends refractometer occassionally as well as knowing what they should read when I mix up a new batch of salt water. I use 2 so if one was to go crazy for some reason I always check the water with both and make sure they are off the right amount. One reads .004 low and the other reads .002 low. (At one point I had a s.g. of around 1.030 thinking it was 1.026!)
I think you would be happier with the refractometer. As far as the diffence between the $125 version and the $85 version I couldn't tell you much there.
FWIW, Nathan

[Kengar]

difference in price may be attributable to one being design to compensate for temperature automatically (which means you can measure the s.g. at temps other than e.g. 77 and rest assured you are getting the right reading). I believe all floating hydrometers will vary widely in the s.g. value they give you depending on the temperature, which means you either drive yourself crazy trying to get the water to the right temp to measure (before you go dumping it into your tank) or figure out the amount of error value for the temp you actually measured at. Either way a pain. Get the refractometer; you'll be glad you did.

[Pairadize]

Take the guess work out of the equation....Get a refractometer. Spend it now, or lose it later in dead animals. Save yourself the headache.

[Brad Ward]

I have found the Tropic Marin hydrometer to be accurate enough for my use. npaden, an easy way to use it is to fill the plastic tube it comes in with the water to be tested and that way you can test w/o it moving around. I do like the ease of using refractometers as well, but just haven't bought one for my personal use. Remember that refractometers need to be calibrated though. I can remember more than 1 time when one I used drifted away from accurate and less than natural seawater was being mixed for a long time ;).

[hughem]

I use a floating hydrometer. Mine is calibrated at 75 degrees. I used the common chart (copied in Shimek's article on Salinity and Temperature):
(of course, the tabs get hosed, but here it is)

Fahrenheit Celsius 1.020 1.021 1.022 1.023 1.024 1.025 1.026 1.027
74.0 23.3 28.0 29.3 30.6 31.9 33.3 34.6 35.9 37.2
75.0 23.9 28.2 29.5 30.8 32.1 33.5 34.8 36.1 37.4
76.0 24.4 28.4 29.7 31.0 32.3 33.7 35.0 36.3 37.6
77.0 25.0 28.6 29.9 31.2 32.5 33.9 35.2 36.5 37.8
78.0 25.6 28.8 30.1 31.4 32.7 34.1 35.4 36.7 38.0
79.0 26.1 29.0 30.3 31.6 32.9 34.3 35.6 36.9 38.2
80.0 26.7 29.2 30.5 31.8 33.2 34.5 35.8 37.1 38.5
81.0 27.2 29.4 30.7 32.0 33.4 34.7 36.0 37.4 38.7
82.0 27.8 29.6 30.9 32.3 33.6 34.9 36.3 37.6 38.9
83.0 28.3 29.8 31.2 32.5 33.8 35.2 36.5 37.8 39.2
84.0 28.9 30.1 31.4 32.7 34.1 35.4 36.7 38.1 39.4
85.0 29.4 30.3 31.6 33.0 34.3 35.6 36.9 38.3 39.6
86.0 30.0 30.5 31.8 33.2 34.5 35.8 37.2 38.5 39.8
87.0 30.6 30.8 32.1 33.4 34.8 36.1 37.4 38.8 40.1

I use a graduated cylinder to float it. The only disadvantage I see with hydrometers is that the reading is hard to get accurately because of surface tension on the water -- it is hard to determine where the water hits the scale; from under water it appears to "wick" up, but from the surface it appears to wick down. Also Murphy always has his way, and the unit rotates with the scale away from you. :)

[ric]

Save money and time go with the refractometer. You will be glad you did. I got mine at Marine Depot for $85.

Ric

[Sparrow]

Hi,

I have both a refractometer and TM hydrometer, though now I use the refractometer exclusively. Since money is not an issue that get the refractometer. The TM hydrometer is not a bad choice but you need a graduated cylinder or some sort of container to get an accurate measurement.

The refractometer I find is just more convenient. It allows me to take small water samples - 3 to 4 drops. This is especially useful when you need to know the salinity of newly bought corals or fish and there is not enough water to fill the container. hth.

[Snailman]

We have two of the Tropic Marins and they rest comfortablly in their cases since we got our refractometer last year. :)

[jackson]

I bought an Aq. Systems hydrometer and it broke when I tapped it to dislodge air bubbles so I got a used Pinpoint salinity monitor. I like it and I think it is very accurate and I only paid $30 for it. I calibrate it before I use it, takes only about a minute, and I check my salinity every week or so just to be sure it's OK. Is the slainity monitor properly calibrated more accurate than a refractometer?

[ngreene]

Get the refractometer, you will be happier and it is easy to use!!! No questions asked. More then worth the money.

I have had the Pinpoint pH probe (which you need to convert), and the silly plastic units. And while the plastic units work, its just not worth the chance on a large tank to misconvert something like your salinity.

I love it and would never go back.

[Staceon]

Hi Keith,

I have the refractometer that you spoke of from PA. I also believe that yes the one at Marine Depot is the exact same thing. IMO its worth the money. Once you close your eye and take a look into that device you will not want to go back.

[LgIslandreefers]

schrodi,

I too am interested in purchasing a reftactometer. Could you post where you saw it for $85. I checked Marine Depot an they have it listed for $115.

Thanks

[Ironreef]

I have a refractor but I calibrate my hydrometer what every few mo. its easier to use. My intent being if your LFS has a refractor or if you know someone with one the cheap route would be to calibrate a hydrometer. They are pretty accurate even though they maybe off. IME its not that big of a deal to have salinity right on= 1.022-1.028 would be okay you just need to know where you stand.

[schrodi]

Norcoast Marine has them for $85.00 There website is:

http://www.northcoastmarines.com/refract.htm

[Tadashi]

Does anyone know about the quality differences PA talks about with the cheaper models? Has anyone seen the differences?

Just got an e-mail from Northcoast. They also have a 1 year warranty and are made in China. Where are Aquamarine's made?

[Edited by Tadashi on 02-13-2001 at 07:25 AM]

[LgIslandreefers]

schrodi,

Thanks for replying. I just wanted to let you know, I called Marine Depot and they matched Northcost price for the refractometer, so I ordered one as well as a pinpoint ph monitor.

[Oppsea]

Hi All.

About the electronic salinity probes, here is a note on that. A couple of years ago I called the manufacture of the equipment, name left to the imaginative. After several pressing/probing ;-) questions I posed, I was confirmed in my conclusions. The electric salinity probe is a conductivity probe arranged & calibrated to show salinity, at some specific set of water conditions. What that meant to me was the salinity reading was only as good as the other water quality conditions. So the salinity and the other water content (dissolved solids etc) were not separated, as is done to a much greater extent in a refractometer. So I got the refractometer, happy with it, although it would be nice to have an electronic display like temp, ph etc.

[Snailman]

ngreene



[welcome]

[Snailman]

Oppsea




[welcome]

[fish5128]

Here's a few things for you:

The refracts from North Coast Marines do have auto temperature compensation. They are manufactured in China (I believe so are every one elses).

I just hate it when someone else drops their prices just to match ours.:) Why didn't they offer it to you at that price to begin with?


http://www.northcoastmarines.com

[LgIslandreefers]

northcoast,

Why didn't you offer it for $70 in the first place, just kidding. Sorry I didn't order from you guys, but i just found out about your site. I have been deealing with Marine Depot for some time now and they have really been outstanding. I have book marked your site for future reference.

[zerrez]

Just want to let everyone know I just ordered a refractometer from Northcoast and he sold it to me for 70.00 just like he said. Its supposed to be the same one PA sells and its got the temperature compensator. So thanks Marc for the nice price.

[Northern Reef]

Sorry guys, no commercial posts on this board.