Reef Discussion

parrdog

Member
Sep 19, 2011
349
125
Engadine
Why Is My Salinity Rising?
G'day Guys,

I'm having trouble with my salinity. It keeps rising. My ato seems to be working fine as the water level remains constant. I tested the ro in my ato resovoir and it has a salinity of 0ppt.

I have been dosing Kent Tec M which is known to raise salinity. I haven't dosed it for 2 weeks though. I was dosing it to combat bryopsis and it is now under control. The mag level at the moment is about 1700. I plan to let it come down gradually on its own through water changes etc.

I recently started dosing Red Sea Foundation supps A and B (Calcium and Alk) using a dosing pump. The doser doses 35ml of each a day (the doser spreads out this amount over 6 dosings). I have also started using ZeoVit Start and Bak. I am dosing this very gradually.

Ok, my salinity. A few days ago, I noticed it was 37ppt, when earlier that week it was 35ppt. I use a Hanna Seawater Refractometer. I took out some saltwater and replaced it with ro. The next day it was 33ppt. After doing nothing, the next day it was 34ppt. Today it is 35ppt.

Obviously this is stressing me out and the corals. All these swings are making them quite grumpy :(.

Any ideas as to what might be going on? My first port of call is to ask Ads if I can compare refractometers with him to rule out equipment error.

Thanks guys,
Jamie.
 

Sarg

Member
Dec 11, 2011
2,559
926
Cheltenham
I'm not familiar with the Hanna refractometre but with my atc I calibrate it with ro before each use as it is always manages to get out of wack between uses. Might be something to try if your not. I know you can by calibrating fluid to so you get an exact 35ppt reading.
 

MagicJ

Moderator
Jul 11, 2011
9,651
3,761
Hobart, Tasmania
Your refractometer may not be calibrated correctly, but as you are measuring the same water any error should not be an issue.

I am aware that dosing Randy's Recipe does increase salinity over time, as it happened to me :banghead Your Red Sea products are effectively the same and so that may be the cause but I would not have thought the increase would be as sudden as you are experiencing.
 

rnscross

Member
Jul 16, 2011
161
107
how much skimmate are you pulling out? as generally this will contain less salt than in the rest of the water, if you're runnig your skimmer really wet this could be causing your problems.
 

MagicJ

Moderator
Jul 11, 2011
9,651
3,761
Hobart, Tasmania
how much skimmate are you pulling out? as generally this will contain less salt than in the rest of the water, if you're runnig your skimmer really wet this could be causing your problems.
But, with an ATO operating, wouldn't this result in a reduction in salinity rather than an increase?
 

parrdog

Member
Sep 19, 2011
349
125
Engadine
Thanks heaps sarge, Magic and crossy, I really appreciate your comments :).

I'm hoping that this can be put down to user error on my part.

I'm heading over to Ads' tomorrow, so we can check my readings on my refractometer compared to his.

I'll report back with the goss.

Thanks again,
Jamie.
 

MagicJ

Moderator
Jul 11, 2011
9,651
3,761
Hobart, Tasmania
Jamie, I am sure that you have been around long enough to read a refractometer so I doubt it is that. Hopefully it is that simple but I have my doubts.

Do you clean off/dry the refractometer after you have used it?
 
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parrdog

Member
Sep 19, 2011
349
125
Engadine
Thanks Magic, it was user error so I'm happy :).

My refractometer is electronic. My mistake was not letting it sit for a minute or so so the temp of the device stabilised with the temp of the water being tested.

Cheers for the help guys :).

Jamie.
 

NiCd

Lead Moderator
Jul 29, 2011
4,297
1,586
Sydney
interestingly we made up a reference solution and the digital tested low by one ppt and my traditional one tested high by one ppt

Having said that we did not bake the salt before hand so his was probably spot on.

I am raising my salinity off the back off it
 

rnscross

Member
Jul 16, 2011
161
107
also the reasdings will be based on the water being at 25C any differences in temperature will also make a difference to the reading.
 

NiCd

Lead Moderator
Jul 29, 2011
4,297
1,586
Sydney
Both have automatic temperature compensation but the digital calibrates to the ambient temperature first, when you add the sample you need to wait a little bit for it to read and then adjust to the temperature of the sample water.
 

rnscross

Member
Jul 16, 2011
161
107
Both have automatic temperature compensation but the digital calibrates to the ambient temperature first, when you add the sample you need to wait a little bit for it to read and then adjust to the temperature of the sample water.
I thought that standard light refactometer had to be read at 25C for it to be completely acurate. Allowing for the water to be the same ambient temp as the refractormeter helps to minimise distortion but doesnt remove it. Or is this a new type?
 

NiCd

Lead Moderator
Jul 29, 2011
4,297
1,586
Sydney
If you spend a bit more money on your refractometers you can get ones with atc or automatic temperature compensation. This generally gives a wider range has of 10-30*c, but I haven't seen too many that go over 30*c.

The issue is generally less with the temperature of the water and more to do with the temperature of the refractometer. If you place one drop ie .05mls of water at 25*c onto a glass and metal structure that has a mass 500 grams in weight and has a temp of 30*c, what temp do you think that sample water will be within 10 seconds?
 

rnscross

Member
Jul 16, 2011
161
107
I was more saying having the ambient temp at 25 (and so the refractometer would be to) would be important for the reading. didn't know there was atc refractometers, pretty cool actually. Also a digital reading of salinity is based on electrical resistance and temperature will also have an impact on that, although to what degree I dont know. Lol this has kind of gone off topic, but I've learnt something new!

NiCd where would I get one and which brands are atc?
 
Do not put too much faith in Digital specific gravity meters !
I had one ,a "Scionix SSG 1000" from "Hinterfeld" ,measured 1.021and was actually 1.026
setting at 1.025, was acually 1.030
Corals started to droop ,but was able to diagnos the problem with a back up Refractometer and add heaps of RO water to drop level of salt content
further to the story Hinterfeld offer a 12 month warranty but did not want to offer any assistance within that time