Contradicting salinity readings

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I have a "Milwaukee" reefracotor meter and according to its readings keep my salinity at 1.025. I have 6 small fish and the beginnings of star polyps in my 200 litre system.
Over the last few weeks my star polyps started to "dissapear" or disintegrate.
Had the water tested only to be told their reading for salinity was 1.020. They used 2 different reefractor meters but not the same make as mine. After a panic attack and then driving to the opposite end of the penninsula I got another reading for the same sample of water. This reading matched mine and was taken with the same make as well. When comparing readings from both our reefractor meters I came to the conclusion that according to my OWN meter, I should get a reading at say 1.028. This is not to say that my reading 1.028 will be the same as someone elses of also 1.028.
Has anyone else got the same discrepincies? There I thought my salt levels were fine.
Moral of story is to take your own salinity meters to the shop you plan to purchase your stock from and take a reading of their water in their tanks and make sure your own tanks at home are the same.
 
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I took a reading over the week-end which said zero. I will do another one tonight. I was told and have'nt calibrated the unit either on the assumption that ALL RO is zero.
My saying is never assume.
 
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Gemma i created a huge disaster when i basically RO dipped my whole tank for a week as i never cleaned my refractormeter correctly, and nevre calibrated with RO as Thalion has suggested. i had a salt residue on the glass leading to higher than actual salinity and a major problem in my tank.

i would suggest a RO callibration first, and then check your readings. then take it to another reefer again and check against these again. Running marine tanks without salt doesnt really work that well. I tried:(
 
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Yup, refractometers are not all their made out to be... I do ude a refractometer for "everyday" use, but still use a glass hydrometer to verify the reading every now and then. Refractometers should ideally be at the same temperature as the water being tested, and MUST be calibrated with RO water before every test, as they do tend to "drift".

Hennie
 
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I was going to say exactly that. The big glass hydrometers used in the chemical industry but also available in LFS's are much more reliable than a refractometer. Also much more breakable, I have one stuck away and use it to check that the refractometers are working.

The little hydrometers that come with thermometers are not what I'm talking about, although, if kept clean they are consistant. Might wrong consistantly , but consistant.:)
 

jacquesb

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JIP! Ditto - refractometers are not ALWAYS what they are made out to be!

Not bad to have one - quite cool though. BUT - I have quite a bit of success WITHOUT ONE.... I use an old swing needle hydrometer.... BUT - I have learnt to "read" my tank - and knows what salinity (plus-minus) my tank is at, at what level the water is in the last compartment in my tank's sump...... I measure my salinity once a week these days...... and I have noticed that my "guesstimates" are rarely wrong.....

So - EVERY INDIVIDUAL get's to know their system/s, if they do not change systems too often.....
 
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I once dropped my refractometer (Deltec) while unloading my car. It was still in its casing with thick foam padding. Nevertheless i still inspected carefully for damage, found none and then forgot about the incident. A few days later while mixing water for a water change i checked the salinity of the DT. My lips went dry, my tongue went numb and i popped a few blood vessels. :035:I had a reading of just over 1...This could not be happening.

It was only after checking my other tank that i realised that it could be the refractometer.

Now i do as Shaun suggests. I check with RO.
Personally i never liked the glass hydrometers. Preferred the swing arm type.
 

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