Hydrometers

[BtmDweller]

Hey peoples, just wanted to share a recent issue I faced.  For starters I have used one of the cheap $10 Instant Ocean hydrometers for years (20+).  I have no idea how these can be near accurate, but it's worked for me.  I've been pleased to know it's cheap, easy, and has been reliable.  Reliable for me is any fluctuation within 1.021-1.024.  I have an apex, but could never get the salinity probe to calibrate, and have a hard time trusting it (calibrated several times with no success).  Maybe it's my tank, who knows.  Anyways, I started using a Hanna battery operated hydrometer just cause.  I've checked salinity for about two months following calibration, and during calibration checked against the instant ocean cheap $10 "dump in the tank plastic awesomeness" as well as a "hey I want to be a scientist" refractometer.  For the past couple months, the Hanna tester gave the same reading 30ppt/1.022-23 which was cool, until it wasn't.  Yes I could have calibrated it more often (I'm a lazy reefer, plus full time Master's student/work/housing projects). For the past few weeks I noticed some corals fade, including a 3 year old colony.  Initial thought ca/alk was off, checked more closely and adjusted slightly.  A little better, but still not great, so pull out the $10 hydrometer and my salinity was sitting at 1.016.  Again I'm not anal with salinity, but crap!  So now what?  Add a bunch of salt, but then the para swing a bit more (a lot more!) than I anticipated.  So what next?  Stop dosing, until it settles and hope for the best.  So far damage control minimal, lost a harder to keep acro mini colony, and a chalice isn't looking its best (not bad for 150+ frags and corals).  Maybe there's something in my tank throwing off calibration to the apex probe and Hanna, likely.  Just wanted to share the experience in the event it's helpful. 

 

 

[treesprite]

I would never trust a hydrometer to be accurate. I used them for years and no two ever gave the same reading. When I moved in April, I threw away 4 different ones that were in the old tank junk. Two of them had lines drawn for where 1.026 would be, because the reading was off by a certain specific amount every single time. If I just had a FO tank, a hydrometer would be good enough, but with corals, it wouldn't be the safe route to take.

[Yachaq]

Thanks for sharing. I have the Hanna salinity checker and have found it reliable so far (around 3 months or so). I am careful to calibrate it monthly and rinse with RO after using it. I have also used a manual refractometer which I calibrate every time with 35ppt solution. It was interesting (and annoying) to see the swing in calibration from use to use. Sometimes the refractometer will be ~4ppt off the mark. I have never used an hydrometer, but I read about their variability. I also don't rely on the Apex probe for fine tuning salinity, as it is off the mark no matter how I calibrate it. For me its mostly and alarm indicator for something going sideways.

 

An option you could try is the Milwaukee digital refractometer. It requires a calibration with distilled water before each use, but it takes less than 10 secs to do it.

Hope your system regains stability soon.

[Origami]

Get a temperature compensated refractometer and some quality calibration fluid that you can use to double check measurements. I never put my full trust in a single device.

Your trusty old hydrometer may be giving you a better reading, but you can never tell. Plastic expands with temperature and some may absorb small amounts of water that can cause the indicator to swell or, conversely, shrink. This can cause measurement variation.

Why you're getting such a wide variation between the Hanna and the refractometer is unknown. One of them is lying to you. Find another member nearby, or an LFS, that can check a water sample for you, to get another data point and proceed from there. The difference between the readings is too great to jump into making corrections now.

[GraffitiSpotCorals]

Exactly. Can’t trust just one device. I use a refractometer as a backup but calibrate it every use. Can’t use the cheap ones and gotta use 35 ppt.  Now I use a Hanna digital which is good with ro water to calibrate. It’s the best thing I have bought and haven’t had to second guess it for a while. I even have a glass float as a third device to check with. 
All of the crashes I have seen where long time hobbiests have been stumped were from salanity issues from cheap, wrongly calibrated or broken refractometers. It’s sad but it happens to the best of us. 

[BtmDweller]

3 hours ago, Origami said:

Get a temperature compensated refractometer and some quality calibration fluid that you can use to double check measurements. I never put my full trust in a single device.

Your trusty old hydrometer may be giving you a better reading, but you can never tell. Plastic expands with temperature and some may absorb small amounts of water that can cause the indicator to swell or, conversely, shrink. This can cause measurement variation.

Why you're getting such a wide variation between the Hanna and the refractometer is unknown. One of them is lying to you. Find another member nearby, or an LFS, that can check a water sample for you, to get another data point and proceed from there. The difference between the readings is too great to jump into making corrections now.

Good points, one thing I do know is when I'm using the plastic hydrometer and not so recetly calibrated refratometer I'm getting the same numbers (for years) and corals are happy. But that defeats the purpose to have an easy dip and test.  I have cleaned the Hanna well with fresh water after each use.  Just hoped it would hold calibration longer. Awhile back did away with a Hanna Ca tester as well, and stick with salifert test kits. 

 

 

[BtmDweller]

Also I'm assuming that they all are off a little bit. I dont mind a slight variation or salinity swing within reason.  This was just not even close. 

[Origami]

I'm not familiar with the Hanna salinity meter. I have a Milwaukee electronic refractometer and a few handheld refractometers. If I looked hard enough, I might find my original Instant Ocean hydrometer.

It sounds like the Hanna may be the issue here. Is this their handheld conductivity meter? How do you calibrate it? Any chance the calibration fluid is bad? Or, it was left open, it may be more concentrated, which could lead to low tank readings.

[epleeds]

Hanna is the same as the Milwaukee. 

[BtmDweller]

2 hours ago, Origami said:

I'm not familiar with the Hanna salinity meter. I have a Milwaukee electronic refractometer and a few handheld refractometers. If I looked hard enough, I might find my original Instant Ocean hydrometer.

It sounds like the Hanna may be the issue here. Is this their handheld conductivity meter? How do you calibrate it? Any chance the calibration fluid is bad? Or, it was left open, it may be more concentrated, which could lead to low tank readings.

It was brand new.  Initial calibration worked, calibrating in solution. I think it just needs constant calibration. The instructions say monthy or when high accuracy is needed.  

[Yachaq]

The Hanna measures conductivity and needs to be calibrated monthly using their proprietary fluid (~$2.50 each). Milwaukee on the other hand is a digital refractometer that should be calibrated with distilled water. In my short experience they are both reliable although remembering to re-calibrate the Hanna is sometimes a problem for me.

[BtmDweller]

Yup basically, It should be calibrated frequently, and if you want accuracy may need calibration outside a week or two.

[wildcrazyjoker81]

I personally have an 8 year old Vee Gee Refractometer and it has always been spot on with 35ppt reference fluid with no adjustments needed. That said even though it has ATC it seems to not calibrate well unless the reference fluid is closer to the needed 77 degrees. Last week I went ahead bought the Tropic Marin Floating Hydrometer so I had something to use as a separate reference. To my surprise my Refractometer was barely off compared to the floater. Refractor was a hair under 1.026, between 34-35 PPT and floater was two ticks over 1.026 which seems like a close enough outcome for me.

So it seems to me you definitely get what you pay for with the expensive Vee Gee Refractometer.

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