Why does all the products I see recomend such a low salinity?

[Drachs]

The average salinity of the ocean is 35ppt (1.026sg)... So why do all the products I see, such as the salt mix I use and the hydrometers I use all seem to recommend a much lower level of 27-32ppt (1.020-1.024sg)?

What do you guys keep your aquariums at, and why did you pick that level?

[HighlandReefer]

Salinity levels in a fish only system are commonly kept at the lower level you mention. Reef systems are usually kept close to NSW levels.

Randy states in his article entitled, "Reef Aquarium Water Parameters":
http://www.reefkeeping.com/issues/2004-05/rhf/index.php

"Salinity

There are a variety of different ways to measure and report salinity, including conductivity probes, refractometers, and hydrometers. They typically report values for specific gravity (which is unitless) or salinity (in units of ppt or parts per thousand, roughly corresponding to the number of grams of dry salt in 1 kg of the water), although conductivity (in units of mS/cm, milliSiemens per centimeter) is sometimes used.

Somewhat surprisingly, aquarists do not always use units that naturally follow from their measurement technique (specific gravity for hydrometers, refractive index for refractometers, and conductivity for conductivity probes) but rather use the units interchangeably.

For reference, natural ocean water has a salinity of about 35 ppt, corresponding to a specific gravity of about 1.0264 and a conductivity of 53 mS/cm.

As far as I know, there is little real evidence that keeping a coral reef aquarium at anything other than natural levels is preferable. It appears to be common practice to keep marine fish, and in many cases reef aquaria, at somewhat lower than natural salinity levels. This practice stems, at least in part, from the belief that fish are less stressed at reduced salinity. Substantial misunderstandings also arise among aquarists as to how specific gravity really relates to salinity, especially considering temperature effects.

Ron Shimek has discussed salinity on natural reefs in a previous article. His recommendation, and mine as well, is to maintain salinity at a natural level. If the organisms in the aquarium are from brackish environments with lower salinity, or from the Red Sea with higher salinity, selecting something other than 35 ppt may make good sense. Otherwise, I suggest targeting a salinity of 35 ppt (specific gravity = 1.0264; conductivity = 53 mS/cm)."

That said, I keep my level between 1.026 - 1.027

:)

[Bonebrake]

I shoot for 35 ppt because that is the average ocean salinity.

[bertoni]

I think the reason they recommend that level is that they can say that the product makes more gallons of saltwater that it would otherwise, but I'm only being cynical. A long time ago, lower salinity was often recommended, but the reasoning was faulty, in my opinion.

[Billybeau1]

The standard seems to be about 1.024 for most salt manufacturers. I'm not sure what the percentage is of full blown reefers as opposed to fish only tanks that buy synthetic sea salt, but I suspect, like Bertoni, that they are just trying to stretch their numbers. Maybe they already know that there are more FO and FOWLR tanks buying salt then full blown reefers housing corals and such.

Just a theory.

[C. Schuhmacher]

HI

The salinity in the ocean can be different
from 32 some areas in the pacific to 34/35 in the atlantic - 37/38 in the red sea.

A salinity between 32 - 33 is ok and let space for mistakes

greets claude

[HighlandReefer]

I would use a properly calibrated refractometer to determine the salinity levels. The hydrometers can be off significantly.

[C. Schuhmacher]

Hi cliff

Also the refracts can be showed wrong levels
the best way ist the measurement by conductivity.

Greets CLaude

[Boomer]

The original theory behind lower salinity was from Tom Frakes and has nothing to do with claims of a salt making more salt at lower salinity. It has to do with an old , yet unproven theory, that fish are less stressed at lower salinity, so there is less demand/energy required to control osmoregulation. Nowadays, I'm sure it is more of the makes more salt idea, thus false advertizing .

Any "device" can have issue with wrong levels of salinity if not calibrated correctly, to include conductivity meters. However, the most accurate is a meter and is the NSW std for Salinity now. Most condo meters for Salinity are just to expensive for many and are not really needed.

I might add that if you look at a map or check into the Salinity of corals reefs around the world very few have a Salinity of 35 ppt. Most reefs are lower than that. And on most reefs the Salinity changes about +/- 1 ppt during the yearly cycle. The only real reason many of us give 35 ppt is so we are all on the same page.