1.025 vs 35 ppt - often used interchangeably?

[Jax15]

I rejoined the hobby back ~2016, and everyone seemed to agree that 1.025 was the perfect salinity. Lately though, more and more I've been hearing that 35 ppt is what you should target for mixed reef or SPS dom. It's strange to me that these are often used interchangeably, since 1.025 is really closer to 34 ppt.

So which is it these days? Mostly curious, do you tend to target a SG or PPT? What is your preferred salinity? Is 1.025 still the "gold standard"?

 

[Mastiffsrule]

Hi,

I am an old time fish guy, 1.023 steady all day long since 1984.

 

[TheShrimpNibbler]

From what I’ve seen, people shoot for both of them based on what type of salinity measuring tool they have. I don’t really know if one is better than the other.

 

[Michael Gray]

I'm gonna follow. But 35 is common because the natural sea level theory.

I test for 35 and shoot for that. 1.025-1.026 swing I don't think is going to be any issue

 

[jayzapple]

I believe 35 equals to around 1.0264. That's on the high edge and could easily hit 1.027 due to evaporation or mistakes. And I often find read those numbers accurately is so hard.
For easier-to-read and other piratical reasons, I always keep it around 1.024-1.025SG or 33-34PPT.

 

[Tampaman]

My refractometer reads both and as mentioned 35 is equal to 1.0264....which is also the same as my calibration solution. So calibrated at 35 and tank reads 35. If not mistaken, a higher salinity gives your water the ability to hold more calcium before precipitation...and just about every other element.

 

[Flippers4pups]

1.026 was my standard back in the day. 35 ppt now. Same difference. I use calibration fluid at 35ppt for my refractometer. Bi-monthly calibration.

 

[Flippers4pups]

Hi,

I am an old time fish guy, 1.023 steady all day long since 1984.

Nothing like the old school! Lol

 

[SeaJay]

I just got a Hanna salinity tester and was playing with it. I keep my water at 1.025 per a refractometer. The Hanna confirms I’m at 1.025, but when I switch to ppm it reads 31.8.

 

[Flippers4pups]

I just got a Hanna salinity tester and was playing with it. I keep my water at 1.025 per a refractometer. The Hanna confirms I’m at 1.025, but when I switch to ppm it reads 31.8.

PPM or PPT?

 

[SeaJay]

PPM or PPT?

Yeah. Good question. I guess I should go look at that again...

 

[Biglew11]

I use 35 ppt as my measurement. ppt doesn't change with temperature specific gravity does. Although the way we test for ppt with a refractometer is also affected by temperature so there may not be as big a difference as I think.

 

[Homebrewer]

I use 35 ppt as my measurement. ppt doesn't change with temperature specific gravity does. Although the way we test for ppt with a refractometer is also affected by temperature so there may not be as big a difference as I think.

Beat me to it. This is the answer right here. SG is subject to temperature influence. 35 ppt is simply parts of “salt” per thousand parts of solution, in this case, water.

 

[Jax15]

I'm gonna follow. But 35 is common because the natural sea level theory.

I test for 35 and shoot for that. 1.025-1.026 swing I don't think is going to be any issue

Interesting point. But then it makes you wonder, why wasn't the "gold standard" all these years 1.026, if that's roughly 35ppt or NSW? Why did the community tend to drop it down to 1.025? Seems strange, or at least arbitrary.

 

[Jax15]

My refractometer reads both and as mentioned 35 is equal to 1.0264....which is also the same as my calibration solution. So calibrated at 35 and tank reads 35. If not mistaken, a higher salinity gives your water the ability to hold more calcium before precipitation...and just about every other element.

Thanks Tampaman, this is probably the best theory I've heard yet. Explains why most salt mixes recommend 35ppt, and not 1.025 SG.

For the record everyone, I keep my reef at 1.025 SG, or around 34 ppt. I've considered raising it to 35 ppt to match my salt mix (blue bucket), but then again... refer to my original question .