Red Sea salinity conversion discrepancy?

[KnightlyBuzz]

Per Red Sea Blue Bucket an SG of 1.0255 = 35.5 ppt (see attached, corals row). However, per my refractometer scale and many conversion calculators (see attached reefapp calc) an SG of 1.0255 = 33.8 ppt.

35.5 ppt = 1.0255 SG (Red Sea Blue Bucket)
33.8 ppt = 1.0255 SG (refractometer & reefapp)
35.5 ppt = 1.0268 SG (refractometer & reefapp)

Since I’m a rookie this confuses me, I need some help please.

 

[Ron Reefman]

IMHO the difference between 1.025 and 1.026 or even 1.027 or 1.024 is not that significant. Maintaining a stable number is more important than the actual SG level.

Find a refractometer or hydrometer you like, learn to use it properly and keep it calibrated and then keep your salinity (SG) stable.

I have 2 tanks and my salinity can vary a bit from time to time. I try to stay in the 1.025 to 1.026 range. But I have seen it go to 1.024 or 1.027 on occasion. It's not that big a deal.

 

[KnightlyBuzz]

So since Red Sea recommends 1.0255 SG (left side of my refractometer) and 35.5 ppt (right side if my refractometer), should I just split the difference and go in between those two numbers?

Also, how does a big company like Red Sea make a mistake like that? It bugs me, can you tell? LOL!

 

[Dr. Jim]

I don't have a perfect explanation for you but think I can steer you in the right direction.
Red Sea is measuring DENSITY when we are measuring SPECIFIC GRAVITY. (Here is where I can't give a perfect explanation, but you can read about it if you google "density vs specific gravity."

Density vs Specific Gravity
Density is the material per unit volume while specific gravity is the ratio of the density of a substance to the density of a reference substance. The key difference between density and specific gravity is that density is an absolute value, while specific gravity is a relative value for a substance.

So, the amount of salt in water can be measured in different ways. All of the following are conversions for the same sample (at 25 degrees Celsius):

-Conductivity: 52.0
-Density: 1.0227
-Specific Gravity: 1.0258

You may also want to look at some online calculators. Here is one:

Salinity calculator

A unit converter for calculating salinity in marine aquariums. The calculator supports conductivity (mS/cm), salinity (PSU og ppt), density (g/cm³) og specific gravity.

reefapp.net

Hope this helps.

 

[Randy Holmes-Farley Verified Community Expert]

Per Red Sea Blue Bucket an SG of 1.0255 = 35.5 ppt (see attached, corals row). However, per my refractometer scale and many conversion calculators (see attached reefapp calc) an SG of 1.0255 = 33.8 ppt.

35.5 ppt = 1.0255 SG (Red Sea Blue Bucket)
33.8 ppt = 1.0255 SG (refractometer & reefapp)
35.5 ppt = 1.0268 SG (refractometer & reefapp)

Since I’m a rookie this confuses me, I need some help please.

Red Sea has the conversion for salinity to specific gravity slightly wrong. No idea why, but many aquarium supply companies have imperfect claims.

 

[KnightlyBuzz]

Thanks guys.

Bottom line, what do “the experts” say is ideal?

- 1.025 SG ? (vivid aquariums, and alot of people here on reef2reef)
- 35 ppt ? (I can’t remember where I read this, but I see it alot)
- 33 ppt ? (seems I’ve heard some advocate this, but seems kinda low based on the majority of reefers)

Or simply like Ron Reefman said, just pick one and go with it. Stability > whatever number you choose?

 

[Dr. Jim]

Just reread your post and see you found a calculator. Skimmed thru it too fast....sorry

 

[Randy Holmes-Farley Verified Community Expert]

Thanks guys.

Bottom line, what do “the experts” say is ideal?

- 1.025 SG ? (vivid aquariums, and alot of people here on reef2reef)
- 35 ppt ? (I can’t remember where I read this, but I see it alot)
- 33 ppt ? (seems I’ve heard some advocate this, but seems kinda low based on the majority of reefers)

Or simply like Ron Reefman said, just pick one and go with it. Stability > whatever number you choose?

'Ideal" is a very different question than whether they have the conversion correct, and far harder to answer.

I'd recommend aiming for 35 ppt, but I seriously doubt you'll ever notice a difference in tank creatures between these values, especially if you independently control the most critical parameters, such as alk, calcium, magneisum, and potassium.

 

[Randy Holmes-Farley Verified Community Expert]

I don't have a perfect explanation for you but think I can steer you in the right direction.
Red Sea is measuring DENSITY when we are measuring SPECIFIC GRAVITY. (Here is where I can't give a perfect explanation, but you can read about it if you google "density vs specific gravity."

Density vs Specific Gravity
Density is the material per unit volume while specific gravity is the ratio of the density of a substance to the density of a reference substance. The key difference between density and specific gravity is that density is an absolute value, while specific gravity is a relative value for a substance.

So, the amount of salt in water can be measured in different ways. All of the following are conversions for the same sample (at 25 degrees Celsius):

-Conductivity: 52.0
-Density: 1.0227
-Specific Gravity: 1.0258

You may also want to look at some online calculators. Here is one:

Salinity calculator

A unit converter for calculating salinity in marine aquariums. The calculator supports conductivity (mS/cm), salinity (PSU og ppt), density (g/cm³) og specific gravity.

reefapp.net

Hope this helps.

FWIW, I do not think that this calculator has correct sg values either.

Now that I look at it, i'd avoid this calculator. There are strange issues such as the idea that conductivity changes with temp. It is always automatically corrected by the measuring device.

 

[Dr. Jim]

FWIW, I do not think that this calculator has correct sg values either.

Now that I look at it, i'd avoid this calculator. There are strange issues such as the idea that conductivity changes with temp. It is always automatically corrected by the measuring device.

Oh boy....I really should have kept my nose out of this one!

Thanks for checking on it, Randy.

 

[Randy Holmes-Farley Verified Community Expert]

Here's a better calculator of salinity to sg. Be sure to set the temp of the water and the temp of the reference water to the same temperature, not the default temps.

Using it, one can see that the sg of 35 ppt seawater at the same temperature as the fresh water standard is 1.0264 near reasonable tank temperatures (e.g., 25 deg C).

Sea Water - Equation of State Calculator - TEOS-10 & IES-80

BS Seawater calculator, TEOS-10 - IES-80. Compute the Density, Salinity, Conductivity with the most recent method

monrecifamoi.saulme.fr

 

[KnightlyBuzz]

Awesome, thanks again everyone! 35 it is.

 

[JimWelsh]

Interesting thing the Reef2Reef site did with Bernard Saulme's initials in the meta tag:

 

[KnightlyBuzz]

LOL

 

[Randy Holmes-Farley Verified Community Expert]

Interesting thing the Reef2Reef site did with Bernard Saulme's initials in the meta tag:

lol

 

[Randy Holmes-Farley Verified Community Expert]

I tried to report this to the admins, and report replaced every mention of B S initials to crap, making the report nonsensical:

" It took the guys initials of crap, and converted it into "crap" so it now reads crap seawater calculator instead of crap seawater calculator lol "

 

[Raven09]

Per Red Sea Blue Bucket an SG of 1.0255 = 35.5 ppt (see attached, corals row). However, per my refractometer scale and many conversion calculators (see attached reefapp calc) an SG of 1.0255 = 33.8 ppt.

35.5 ppt = 1.0255 SG (Red Sea Blue Bucket)
33.8 ppt = 1.0255 SG (refractometer & reefapp)
35.5 ppt = 1.0268 SG (refractometer & reefapp)

Since I’m a rookie this confuses me, I need some help please.

This all sounds good. BUT where on the blasted RedSea Salt bucket do you find the mixing quantities. Like how much RO water to salt?
So you want 34ppt and to come close to that number “mix ??? gallons of water to ??? RedSea Coral Pro Salt. Please help, because I have to mix in order to raise salinity.

 

[KnightlyBuzz]

I use Red Sea blue bucket, not coral pro, and for blue bucket it’s approximately 1 cup salt per 2 gallons of water for 34 ppt.

So maybe try 3/4 cup salt per 2 gallons water, and then test it? (Add more water or salt depending.). Nice thing is you do it once and then you’ll know. Sorry, I couldn’t help you more, I have been afraid to try the higher alkalinity of coral pro. Yeah, it’s frustrating/odd they don’t tell you on the bucket.

 

[Raven09]

I use Red Sea blue bucket, not coral pro, and for blue bucket it’s approximately 1 cup salt per 2 gallons of water for 34 ppt.

So maybe try 3/4 cup salt per 2 gallons water, and then test it? (Add more water or salt depending.). Nice thing is you do it once and then you’ll know. Sorry, I couldn’t help you more, I have been afraid to try the higher alkalinity of coral pro. Yeah, it’s frustrating/odd they don’t tell you on the bucket.

Thanks a lot!! Then maybe I’ll use ½ cup salt to 2 gallons of water in order to hold back the alkalinity level. Or will it? What do you think?

 

[KnightlyBuzz]

Most important I think is to hit your salinity. You have to do that, no choice really. Your alkalinity will be what it will be based on the design of the salt formula. There are definitely advantages to the Coral Pro formula, the biggest advantage is they have proved that corals grow faster with higher alkalinity. However, I personally believe that’s good for people with lots of experience in reefing, who can react quickly and know what to do if something goes wrong. But for me just learning, slow and steady is what I’m trying to do. So don’t think I’m saying Coral Pro is bad, I’m not saying that, I’m saying I don’t think I have the experience to use it yet. (For example, I’ve heard in some circumstances the coral skeleton can grow faster than the rest of the coral and create problems like that, and I wouldn’t know what to do about it.)

Sorry for being so wordy, I just wanted you to know where I was coming from. I’m just a new guy trying to help, but I don’t know to much, ha!