This is why I don't trust plastic hydrometers.

[human]

I accidentally broke my refractometer and had to rely on the hydrometers I had lying around. Both were washed with vinegar and rinsed thoroughly with RODI water. Both were filled 3 times and then allowed to settle for a few minutes on a level surface, and both have different readings from the same water source. I'm just posting this to let anyone know that uses these to measure salinity, that your readings may be off. Refractometers are a lot more inexpensive than they used to be and a lot more accurate than these. I believe they're a vital piece of equipment for this hobby. These hydrometers may only be off a few points, but it leaves you to guessing which is right or if it's an estimate of the two, and as we all know, some of our inhabitants aren't to keen on fluctuations in salinity.

 

[cloak]

When you left them alone for a few minutes did you use a chopstick or something and give the needle a few nudges? You might not see them, but doing this a few times will help dislodge any micro bubbles that might be attached to it.

 

[human]

When you left them alone for a few minutes did you use a chopstick or something and give the needle a few nudges? You might not see them, but doing this a few times will help dislodge any micro bubbles that might be attached to it.

I always tap them to dislodge bubbles, then let them settle.

 

[AllSignsPointToFish]

I just got my refractometer today, and it read 0.02 SG higher than the hydrometer. That was a difference between 1.026 and 1.028!

 

[ndz98]

I gotta say, every time I've used my refractometer and my hydrometer they've been pretty dang close. That hydrometer you have on the right looks older due to the fading numbers. Maybe that could be part of the problem?

 

[revhtree Verified Admin]

Thanks for the reminder!

 

[furam28]

We talk about swings in alk, cal, ph... when you have swings like that in salinity you are swinging everything. Never good for corals. When i got my refractometer it read 1.029 on what was 1.026 on the hydrometer. Oops!! Wish someone had told me this sooner to trash my hydrometer long time ago.

 

[SaltMan]

I have a Milwaukee MA887, it reads all over the place. Even after the distilled calibration it does not give repeatable readings, I don't trust it. Looking for a better replacement...

 

[human]

I have a Milwaukee MA887, it reads all over the place. Even after the distilled calibration it does not give repeatable readings, I don't trust it. Looking for a better replacement...

I've heard good things about Red Sea’s seawater refractometer, that's what I'm going to order.

 

[JRig]

I have two of them that were showing different readings. I took them to my LFS where I bought them and asked which one is right. The guy there checked his refractometer calibration, tested some display tank water and compared it to the hydrometer readings with the same water. Both hydrometers were off. One was reading +.002 and the other -.004.

 

[redfishbluefish]

I have found, when used correctly, that swing arm hydrometers are very consistent. The problem is that that number you see is most likely wrong. I don't mean this as a reason to use a swing arm, but if it is calibrated to a refractometer, it could be used in a pinch. You would know, as an example, that the swing arm reading of 1.023 is actually 1.026 on a refractometer. I've been using a refractometer for my entire salt life, except for the first month or so. So I have a swing arm that I just can't throw away.....as a backup if and when the refractometer craps out.

 

[human]

I have found, when used correctly, that swing arm hydrometers are very consistent. The problem is that that number you see is most likely wrong. I don't mean this as a reason to use a swing arm, but if it is calibrated to a refractometer, it could be used in a pinch. You would know, as an example, that the swing arm reading of 1.023 is actually 1.026 on a refractometer. I've been using a refractometer for my entire salt life, except for the first month or so. So I have a swing arm that I just can't throw away.....as a backup if and when the refractometer craps out.

I know one of these is pretty close, I just can't remember which one. You're right about consistency, once I get a new refractometer I'm going to mark both of these just so I have a back up, just incase my clumsiness causes me to break another refractometer.

 

[SDguy]

These types of hydrometers are precise more than accurate. Once you get their correction factor when compared to something like a refractometer, you are fine.

 

[Majikou812]

Here is the thing you also need to remember. When we get a reading from our instruments, whether true or not, they are typically consistent with itself. So for example, if you are using your hydrometer and it gives you a reading of 1.026, the chances of it consistently doing so is very high. With this, your corals and other life in the tank will prefer consistency to precision. I know for myself, I like both, but i have gone diving in water where fresh water is jutting out into the ocean and the same sea life is there under "their" perfect condition as was the sea life 100 miles away.

 

[SethOF]

I believe that the 2 hydrometers are not level. Try swapping the positions to see whether there is a change.

 

[human]

Here is the thing you also need to remember. When we get a reading from our instruments, whether true or not, they are typically consistent with itself. So for example, if you are using your hydrometer and it gives you a reading of 1.026, the chances of it consistently doing so is very high. With this, your corals and other life in the tank will prefer consistency to precision. I know for myself, I like both, but i have gone diving in water where fresh water is jutting out into the ocean and the same sea life is there under "their" perfect condition as was the sea life 100 miles away.

I'm not arguing about their consistency, they're just not usually accurate. So in the situation I was in when I posted this I had accidentally dropped my refractometer and made new saltwater and measured it with these just to check them to make sure. I've been mixing my saltwater the same way for the last 20yrs, so I have it down to where I can mix it to 1.025 by just measuring it out. The reason I posted this is to make people aware that they may not be getting as accurate a reading as they think they are. Some of the inhabitants we keep do not appreciate even the slightest swing in salinity. Say you only had one of these hydrometers that was off and you bought something that's used to 1.025 and your hydrometer read 1.025, but the salinity is actually 1.028, that is enough to shock some of the less hardy inhabitants.

 

[human]

I believe that the 2 hydrometers are not level. Try swapping the positions to see whether there is a change.

There's no change, the one on the right reads slightly less than the actual salinity and the other one reads higher.

 

[Plunker05@gmail]

When you left them alone for a few minutes did you use a chopstick or something and give the needle a few nudges? You might not see them, but doing this a few times will help dislodge any micro bubbles that might be attached to it.

I have two just like those. About the same difference in the readings also. Both are reading lower than my refractometer which has been calibrated to distilled water and 1.026 calibration fluid. I'll always be Leary of the hydrometers from now on.

 

[Russ265]

hydrometers get a bad rap for user error.

http://www.brewersfriend.com/hydrometer-temp/

i believe the instant oceans are calibrated at 60f.

that is why they are consistent but off from a 78-82f reef.

p.s. that hydrometer on the right looks like you got it from an ancient mayan dig site.

 

[Plunker05@gmail]

I think a hydrometer will work fine if you compare it to a more accurate method and re-mark the thing for future use. I use mine almost daily because I know where the needle should float for the proper salinity. I also cross check my two hydrometers with my refractometer occasionally. I also try to clean my hydrometer very good after every use. They say the most important thing is to keep your salinity stable and consistent with any changes being made slowly and gradually.