The Reef Tank banner

1 - 18 of 18 Posts

·
Registered
Joined
·
920 Posts
Discussion Starter #1
Hey all,

I got a new Hydrometer today because i was a little worried that after several years in storage, my old deep six would be compromised a little. I choose to get an instant ocean one. I just compared the two readings.

Instant ocean: 1.029
Deep 6: 1.021

OK, so what should I trust? I am worried that the SG is too high / low and it is "harming" the bacteria colonization from the LR I just put in. If I trust the high number and add RO, and that reading i incorrect, my real SG would drop to like 1.015. If I trust the low number and do nothing, I may be in reality at 1.029.

Thanks!:confused:
 

·
Registered
Joined
·
393 Posts
take it to the lfs and compare them both to whatever they use to measure. If two of the 3 are very similar, those are most likely the closest.
 

·
Registered
Joined
·
3,787 Posts
Take the water to the Local Fish Store (LFS) and get it tested and then invest in a refractometer . I would never trust a hydrometer . JMO
 

·
Just send me a PM ;)
Joined
·
16,796 Posts
I have one that I got off of eBay a couple years ago. works well for me :)
BTW, it's the same unit as they sell at Drs F&S and MD...
 

·
Super Moderator
Joined
·
22,074 Posts
buy a refractometer
Pretty much my answer too :agree:

I've had something like 4 IO swing arms once(one being brand new/unused in the package),and years ago a former reefing buddy of mine had problems with his tank, and asked for my help. So i brought along my test kit(s) and my assortment of IO hydrom's . It was then we noticed that ALL of our hydrometers were off one direction or the other. We talked to our other buddy who had a retail/wholesale livestock only place and he told us about refracts . He tested my buddy's water, and found the S.G was WAY too high , causing the problems in his tank ,by using a refractometer. He then had us test his water using our collection of refracts, and then testing the same water with his refractometer. He had us mark the spot we decided we wanted our S.G. to be, on those swing arm scales. Granted our readings were consistent, but the S.G they read were all over the range, both high and low. So by adding a mark where we wanted our S. G to be at, we were able to at least know what that level was, until we bought refractometers to replace our bunch of swing arms.

So if anything, compare your readings with that of your local shop's hopefully accurate test device, be it a swing arm or refractometer, and mark what is said to be the level you want, on your stuff, if you are not going to get a refract in the near future.

Sorry for the long spiel, just trying to get my point across :wavey:
 

·
I've got the REEF rash!
Joined
·
61,658 Posts
You can get different readings each time with a swing arm(micro bubbles under the arm can change readings)Ebay has nice refractometers.
 

·
Registered
Joined
·
1,360 Posts
i happen to use a hydrometer thats dead on with my salinity ( seamore and I tested against his refracto). Have always used it because its pretty accurate.
 

·
Registered
Joined
·
55 Posts
I bought my refractometer on ebay for about $30... Looks EXACTLY like the one my LFS sells for $99... only difference is mine goes by .002 ppm but the gap between is almost as big as the one they use... still easily read by .001 between the lines...
 

·
Registered
Joined
·
8,350 Posts
i happen to use a hydrometer thats dead on with my salinity ( seamore and I tested against his refracto). Have always used it because its pretty accurate.
Just because it's accurate today doesn't mean it always will be. Salt buildup and microbubbles can and will change the reading each time it's used. Hydrometers need to be soaked in vinegar and reseasoned occasionally. A hydrometer is seasoned by filling it with saltwater and letting it sit for 24 hours. Even after all that, it's still not going to be as accurate as a refractomer that has been properly calibrated. Properly calibrated means using salinity solution and not RO/DI.
 

·
Premium Member
Joined
·
17,355 Posts
buy a refactometer
check the calibration on it first, but it will be the most accurte (next to bulb-hydrometer w/ built-in thermometer. always check to make the adjustment for temp (remember that SG is affected by increaing temp as it makes the water expand at temps above freezing). This affects the ability of the liquid to refract the light as well.

Temperature is one of the single most important factors influencing accurate refractometer readings and is one of the largest sources of error in measurement. Refractive index is VERY dependent on temperature. It is well known that substantially all materials expand when heated (become less dense) and contract when cooled (become more dense). The speed of light in a liquid increases with temperature, and the refractive index, therefore, decreases.

The amount of error per degree Celsius is different for every fluid and differs for different concentrations of the same fluid.
Temperature compensation relieves the user of the responsibility to measure temperature and apply a correction factor when taking readings. Temperature Compensation Makes The Difference!
The chart compares a temperature compensated MISCO Refractometer (red) to a non-compensated competitor (blue). It is plain to see that at 20 'C (68 'F) they are both correct; however, as the temperature deviates from 20 'C, there is a marked error in the non-compensated instrument.
 

·
Registered
Joined
·
920 Posts
Discussion Starter #18
check the calibration on it first, but it will be the most accurte (next to bulb-hydrometer w/ built-in thermometer. always check to make the adjustment for temp (remember that SG is affected by increaing temp as it makes the water expand at temps above freezing). This affects the ability of the liquid to refract the light as well.
I completely missed your post Tom,

Thanks for the info.

I recieved my ebay special refractometer today. It has ATC on it as well...which is cool I suppose. I says to only calibrate it at 72 degrees or something like that. I checked it with some RO (didn't have any distilled) and it is dead on.


This is sooo much nicer then either of the deep six or the instant ocean hydometers.

My SG is 1.025 :)
 
1 - 18 of 18 Posts
Top