SG of natural sea water?

[virginiadiver69]

What is the SG of natural sea water?

[birdfish]

Most important is that there is not one salinity, or temperature, in the various oceans of the world.

According to the chart in "The Marine Aquarist's Manual" by Hans Baensch published by Tetra 1983 (on page 71):
Pacific: 1.021, Indian: 1.023; Caribbean/Atlantic 1.024, and the Red Sea: 1.027.

So if your intent is to keep Red Sea fish, what you would want would be quite different from if you are going to keep Pacific fish.

birdfish

[virginiadiver69]

Thanks birdfish,
That was actually a better answer than I was hopping for. I do plan on keep a pacific tank. Would I be better off keeping it at 1.021 rather than the 1.025 commonly recommended?

[greenbean36191]

Baensch's numbers go against almost every other source on the subject. The worldwide average for reefs is 34.3-35.3 PSU (sg 1.025-1.026) with the highest abundance of reefs being in the Pacific. I used to work with animals from the Red Sea and most sources listed the salinity in the study areas at anywhere from 37-40 PSU (1.027-1.030).

[virginiadiver69]

Okay, then should we be keeping our tanks at the 1.027-1.030 SG? Why or why not?

[Mariner]

Greenbean is right.

Originally posted by virginiadiver69
Okay, then should we be keeping our tanks at the 1.027-1.030 SG? Why or why not?

We should be keeping our tanks as close to what the inhabitants are used to as possible...because that's their natural environment and that's what they're best suited to living in. If you have a tank full of Red Sea animals (which most of us don't) keep it at 1.027+ Otherwise, it looks like most things from the rest of the world's oceans would do best in 1.025-26
Mariner

[Rhodesholar]

To add some personal experience on the matter. I used to use one of those POS swing arm hydrometers and never had any problem. Kept the reef at 1.025 according to it. I started keeping acropora and figured I better be more accurate so I got a refractometer. Tested my salinity, 1.030!!!!

Never had any problems with that high of salinity. I slowly lowered it and now keep it at 1.026. No change. Everything grows exactly the same. Have not lost anything, no better or worse PE. Nothing changed.

[sufunk]

Originally posted by birdfish
Most important is that there is not one salinity, or temperature, in the various oceans of the world.

According to the chart in "The Marine Aquarist's Manual" by Hans Baensch published by Tetra 1983 (on page 71):
Pacific: 1.021, Indian: 1.023; Caribbean/Atlantic 1.024, and the Red Sea: 1.027.

So if your intent is to keep Red Sea fish, what you would want would be quite different from if you are going to keep Pacific fish.

birdfish

Thats weird. We get "natural sea water" supposedly here in the LFS in Fort Lauderdale and its always 1.026-27 not 1.024. I guess maybe some evaporation in the containers raises the SG???

[greenbean36191]

Thats weird. We get "natural sea water" supposedly here in the LFS in Fort Lauderdale and its always 1.026-27 not 1.024. I guess maybe some evaporation in the containers raises the SG???

According to NOAA, the current salinity near Biscayne Bay (so just south of Ft. Lauderdale) is 1.027.

[kelley_mc]

Originally posted by Rhodesholar
To add some personal experience on the matter. I used to use one of those POS swing arm hydrometers and never had any problem. Kept the reef at 1.025 according to it. I started keeping acropora and figured I better be more accurate so I got a refractometer. Tested my salinity, 1.030!!!!

Never had any problems with that high of salinity. I slowly lowered it and now keep it at 1.026. No change. Everything grows exactly the same. Have not lost anything, no better or worse PE. Nothing changed.

Your refractometer isn't one of those cheap blue ones, is it? There have been noted calibration problems with those that make them tend to be off. The cheap ones can't be calibrated to 0 as stated in their instructions but should be calibrated at a higher SG. I forget what it is but there is a thread and recent Reef Keeping article on it.

[RicksReefs]

Originally posted by greenbean36191
According to NOAA, the current salinity near Biscayne Bay (so just south of Ft. Lauderdale) is 1.027.

and my haul of NSW from just north of west palm beach yesterday has a salinity of 1.027 also.

[Paintbug]

heres a great article on this subject.
http://web.archive.org/web/200302181.../1/default.asp

[dippin61]

Originally posted by kelley_mc
Your refractometer isn't one of those cheap blue ones, is it? There have been noted calibration problems with those that make them tend to be off. The cheap ones can't be calibrated to 0 as stated in their instructions but should be calibrated at a higher SG. I forget what it is but there is a thread and recent Reef Keeping article on it.

not quite.. the problems are arising from the calibration solutions being used, and the fact that some people are calibrating with RO water.

Its best to mix up a solution that you know the exact salinity of, like mentioned in the reefkeeping.com article.