salinity - precision and accuracy

[popper]

I had always thought that stability is more important than precision.. I see you and @Slingfox mentioning the need to measure salinity accurately.. can you please guide me why is 35 PSU (1.026 sg) so important? Is it coz they are used to this salinity in ocean? Or the trace Elements are appropriate at that salinity level that keeps the corals happy.. I keep my tank at 1.024 and that might be the actual reason the SPS corals weren’t happy and I have been blaming high nutrients all this while.. honestly, soft corals and LPS seem to be doing great at 1.024




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Alexander1312​

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• Wednesday at 11:12 PM
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• #7

I had always thought that stability is more important than precision..

I always thought this statement was fraught. What's the point of having a stable lack of nutrients, or a stable crazy high amounts of them, or stable out of whack salinity. I think this is just an excuse, for not being able to put in the effort to be precise.

I see you and @Slingfox mentioning the need to measure salinity accurately.. can you please guide me why is 35 PSU (1.026 sg) so important?

Because we obsess over precision. haha. It's really not about 35PSU, 34 or 36 might be fine too. But if I want to set it the global ocean average, you want to have a way to do it. With the current tools, it often seems extremely difficult to get it to a rather precise 35 PSU, which is super frustrating.

Is it coz they are used to this salinity in ocean? Or the trace Elements are appropriate at that salinity level that keeps the corals happy..

There is a few complicated answers to this, suggest to ask AI, but in the most simplest form, yes, this is the reason. Keeping trace elements in optimal ranges is much harder at other salinity levels and if you care about optimal levels, then using 35 PSU is the most established way to dial them in.

I keep my tank at 1.024 and that might be the actual reason the SPS corals weren’t happy and I have been blaming high nutrients all this while.. honestly, soft corals and LPS seem to be doing great at 1.024

Maybe, not sure. My question was sincere, as I never went down that low. For a FOWLR tank ok, but for a reef tank I would go with 35 PSU / 1.0264 sg, and go from there.

150g EXT Innovative Marine Lagoon
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Alex
Walnut Creek

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H2OPlayar​

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• Yesterday at 6:27 AM
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• #8

I had always thought that stability is more important than precision.

It is

can you please guide me why is 35 PSU (1.026 sg) so important?

It isn't.

NASA Salinity: Seasons of Salinity​

Salinity in our ocean has seasonal patterns, rising and falling in one cycle per year
salinity.oceansciences.org
1.023-1.026 is all fine. Some people (above) are taking the reef tank hobby and turning it into a weights and measurements hobby. Cool, go see how precise you can count sodium ions. The science of precision appreciates you. The animals that we are taking care of however, don't care that much what it is, they just like it staying the same so long as it is in an acceptable range. Higher end of the salt/minerals makes it so you are more susceptible to evaporation to get you out of range, and there might be an argument for more availability of minerals for skeletonization, but you could just increase alk and ca and get that independent of the nacl. Low end and you are more susceptible to dilution. BRS put out a good series a few years ago called "Mastering Chemistry" and had 20-30 minute videos that go into the science of all of this. I recommend them. Here is the one on salt

If only PG&E is like a casino. I would have a lot of comps.

Two reasons to move to Vegas, cheaper electricity and comps!

Last edited: Yesterday at 6:44 AM
Thank you,
Michael

Las Vegas 300 Tank
35 Gallon AIO
Sandy 45 AIO Softie Reef
Sandy 120 Reef
120 Freshwater
My Old Home 168
Tank at Fiesta Vallarta

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PizzaOven​

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• Yesterday at 7:10 AM
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• #9

I'm going to be the annoying guy and point out that precision is not equivalent to accuracy. Chasing an absolute salinity (like 35 PSU) is going for accuracy, not precision.

-Andrew

My Red Sea Reefer 250
5g Pico Reef

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Alexander1312​

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• Yesterday at 7:50 AM
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• #10

I'm going to be the annoying guy and point out that precision is not equivalent to accuracy. Chasing an absolute salinity (like 35 PSU) is going for accuracy, not precision.

That's a great point. Unfortunately, when it comes to salinity, there are also precision issues haha.

150g EXT Innovative Marine Lagoon
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Walnut Creek

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H2OPlayar​

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• Today at 8:30 AM
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• #11

I'm going to be the annoying guy and point out that precision is not equivalent to accuracy. Chasing an absolute salinity (like 35 PSU) is going for accuracy, not precision.

Calling out sg at 1.0264 is going for precision. I didn't even know there was a ten thousandths place in numbers.

Thank you,
Michael

Las Vegas 300 Tank
35 Gallon AIO
Sandy 45 AIO Softie Reef
Sandy 120 Reef
120 Freshwater
My Old Home 168
Tank at Fiesta Vallarta

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PizzaOven​

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• Today at 9:45 AM
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• #12

Calling out sg at 1.0264 is going for precision. I didn't even know there was a ten thousandths place in numbers.

That's calling for both precision and accuracy. Calling out "1.0001" would also be going for precision. I think @Alexander1312 is stating that precision alone isn't sufficient.

-Andrew

My Red Sea Reefer 250
5g Pico Reef



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jaysway​

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• Today at 12:03 PM
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• #13

I always thought this statement was fraught. What's the point of having a stable lack of nutrients, or a stable crazy high amounts of them, or stable out of whack salinity. I think this is just an excuse, for not being able to put in the effort to be precise.


Because we obsess over precision. haha. It's really not about 35PSU, 34 or 36 might be fine too. But if I want to set it the global ocean average, you want to have a way to do it. With the current tools, it often seems extremely difficult to get it to a rather precise 35 PSU, which is super frustrating.


There is a few complicated answers to this, suggest to ask AI, but in the most simplest form, yes, this is the reason. Keeping trace elements in optimal ranges is much harder at other salinity levels and if you care about optimal levels, then using 35 PSU is the most established way to dial them in.


Maybe, not sure. My question was sincere, as I never went down that low. For a FOWLR tank ok, but for a reef tank I would go with 35 PSU / 1.0264 sg, and go from there.
Click to expand...

what about the tropic marin hydrometer? i see it gets a lot of hate but I can fill up a 500 ml graduated cylinder from my sump manifold, stick in the hydrometer and measure salinity with reliability/precision in about 45 seconds or less, the temperature is already at 77-78 so i dont need a chart and i never need to calibrate, i have tested two hydrometers side by side and the result was the same.

 

[grizfyrfyter]

This post is interesting but a formatting mess lol
Is this from another thread?

 

[Alexander1312]

This post is interesting but a formatting mess lol
Is this from another thread?

I thought the same thing and then remembered that this was an extract from Max's journal, where we went, as we often do, off topic. So I assume this was an attempt to clean up the journal but it is hard to read now.

 

[Slingfox]

I am paranoid about salinity because when I started the hobby I used a cheapo refractometer which was causing me to run my tank at way too low salinity. I found this out when I was in the midst of a several month battle with the uglies. I wanted to get salinity right since that is one less factor to think about. My struggles were compounded by the fact that I purchased a bunch of instruments (I had six ways to measure salinity at one point including three Hanna Checkers!) and calibration solutions and could not get consistent readings. Eventually I figured it out

If you invest in a reliable way to measure salinity, have an ATO, and replace any volume of skimmate with a similar volume of saltwater, it is very easy to keep salinity at a target range. I have zero idea whether 34 PSU, 35 PSU or 36 PSU is better but I assume any tank will benefit with stable salinity. I prefer 35 PSU since it seems to be the reference standard. I prefer that over 33 PSU or 34 PSU since the higher salinity means using more salt which increases alk, calcium, mag, and traces from the salt mix.

Many people think they keep their tank at 35 PSU / 1.0264 SG, but according to Fauna Marine around 70% of first time ICP customers from the US send samples with too low salinity. In contrast, my last three ICPs show 34.97 PSU, 35.08 PSU and 34.90 PSU. This takes very little money and effort to accomplish but many reefers seem to focus on the latest tech and dosing magic formulas while ignoring something as basic as mixing their saltwater correctly.

 

[Alexander1312]

I am paranoid about salinity because when I started the hobby I used a cheapo refractometer which was causing my to run my tank at way too low salinity. I found this out when I was in the midst of a several month battle with the uglies. I wanted to get salinity right since that is one less factor to think about. My struggles were compounded by the fact that I purchased a bunch of instruments (I had six ways to measure salinity at one point including three Hanna Checkers!) and calibration solutions and could not get consistent readings. Eventually I figured it out

If you invest in a reliable way to measure salinity, have an ATO, and replace any volume of skimmate with a similar volume of saltwater, it is very easy to keep salinity at a target range. I have zero idea whether 34 PSU, 35 PSU or 36 PSU is better but I assume any tank will benefit with stable salinity. I prefer 35 PSU since it seems to be the reference standard. I prefer that over 33 PSU or 34 PSU since the higher salinity means and using more salt which increases alk, calcium, mag, and traces from the salt mix.

Many people think they keep their tank at 35 PSU / 1.0264 SG, but according to Fauna Marine around 70% of first time ICP customers from the US send samples with too low salinity. In contrast, my last three ICPs show 34.97 PSU, 35.08 PSU and 34.90 PSU. This takes very little money and effort to accomplish but many reefers seem to focus on the latest tech and dosing magic formulas while ignoring something as basic as mixing their saltwater correctly.

100%. The only thing I might add is that if you have a heavy two part consumption, like me, your salinity rises rather quickly so skimmate is less relevant in this case and rather beneficial to offset some of this and keeps salinity stable.

 

[H2OPlayar]

50 minutes in they get into this a bit

 

[PjFish]

50 minutes in they get into this a bit

 

[PjFish]

Never dove there but several friends who have reported amazing trips!
How many beautiful corals and fish we keep come from the Red Sea? After a bleaching event a few years ago it had 70-85% recovery rate the highest ever recorded due to record temps..The article link below really doesn’t get into the Red Seas normal high salinity but other articles equate recovery rates and immunities to high salinity averaging around 40 ppt in Egypt/ Saudi Arabia where some of the best reefs are located temps which temps fluctuate 68-85 F annually. Now corals directly from the Red Sea should carry these traits and tolerances kinda makes me want to try a dedicated Red Sea species tank!
One article about the recovery.

Egypt’s Super-Corals Achieve 85% Recovery After Record 2024 Bleaching

The northern Red Sea corals should be dead. By every bleaching model, every thermal threshold established from reefs worldwide, the summer of 2024 should have left them white and dying. Water temperatures climbed to levels that would devastate Australia’s Great Barrier Reef, accumulated heat...

sevenseasmedia.org

 

[Alexander1312]

Never dove there but several friends who have reported amazing trips!
How many beautiful corals and fish we keep come from the Red Sea? After a bleaching event a few years ago it had 70-85% recovery rate the highest ever recorded due to record temps..The article link below really doesn’t get into the Red Seas normal high salinity but other articles equate recovery rates and immunities to high salinity averaging around 40 ppt in Egypt/ Saudi Arabia where some of the best reefs are located temps which temps fluctuate 68-85 F annually. Now corals directly from the Red Sea should carry these traits and tolerances kinda makes me want to try a dedicated Red Sea species tank!
One article about the recovery.

Egypt’s Super-Corals Achieve 85% Recovery After Record 2024 Bleaching

The northern Red Sea corals should be dead. By every bleaching model, every thermal threshold established from reefs worldwide, the summer of 2024 should have left them white and dying. Water temperatures climbed to levels that would devastate Australia’s Great Barrier Reef, accumulated heat...

sevenseasmedia.org

View attachment 79725View attachment 79726

We are not setting up topical fish tanks, but truly follow the ‘mixed reef’ philosophy. I understand freshwater focuses much more on topical arrangements where only species from the same habitant are held together. The saltwater hobby does not appear to have matured in this way.

In the absence of this focus, the average salinity of 35 PSU (34.8 PSU) seems to be the best fit, given how salinity can be very different from ocean to ocean (please ignore the German names of the oceans ...).