High salinity

[zoomonster]

Just looking for a few comments on this subject. I been doing reefs for quite a few years but just coming back from a long hiatus from the hobby.

For many years I ran tanks at 1.022 sg. Typical reef tanks with a large mix of LPS, softies, anemones, inverts and fish and never had a problem. In fact in the case of an ich outbreak a little higher heat and slightly lower SG where always good for a cook off of disease with no detrimental effects to the tank. The higher the SG the more some diseases like ick thrive. Generally speaking 1.022 was the norm (natural seawater ~1.022-1.023) and no one ventured past 1.024.

So I'm a little perplexed with all the people especially new comers running SG of 1.025. I see it mentioned all the time and in sigs. I can maybe see that with the proliferation of people doing (or trying to) SPS but when did a high SG like that become the "norm" and what's the reasoning. I would have to think that SG, at minimum, increases the fish mortality rate.

[bertoni]

The canonical average ocean salinity is 1.0264:

http://reefkeeping.com/issues/2005-11/rhf/index.php#2

That is a good target for marine animals, although the salinity does vary across the world. The Red Sea tends to be higher, for example. I haven't seen any evidence that the lower SG levels are good for animals. I think the common assumption is that animals tend to do best in conditions that are close to their natural environment.

[tmz]

I'm skeptical sg at 1.022 makes any difference for crytocaryon irritans or that higher sg enocourages them. Hypo saline tratments for them drop sg to 1.009 which is the edge of tolerance by marine fish. Ich are present even in brackish water and one study has shown some strain can mutate genrationally to very low sg.

I don't know where the idea that natural seawater is 1.022 /1.023 comes from. I agree with Jon that's the average is 1.0264 with significantly higher levels in some areas like the Red Sea. Some may be lower for a period of time due to estuarial run offs and ice melt in the artic regions.
This is an easy read on point and has more detail on salinity/sg ranges in 77 seas :


https://answers.yahoo.com/question/index?qid=20100915174306AA5jFrr

This is from it:

The salt content of the open oceans, free from land influences, is rarely less than 33 o/oo and seldom more than 38 o/oo

33ppt salinity is 1.0249 sg and 38 ppt is 1.0286. 1.0264 is the average and is 35ppt salinity ; nowhere near 1.022 which is only 29ppt salinity.


Invertebrates including corals are isotonic. They can't osmoregulate like fish can and their internal sg is affected by the water around them as it dilutes or concentrates their internal fluids via diffusion into or out of them..
If their internal sg varies too much they loose homeostasis and perish. I think 1.022 is too low for invertebrates generally.

Invertebrates are best served by sg levels in tune with those they have evolved to live in; 1.026/7 is a good target ,imo. Marine fish with an internal salinity or around1.008 are also built to thrive in higher levels, Long term their internal organs like kidneys may atrophy with less processing activity in lower sg water.

[Randy Holmes-Farley]

I don't know where the idea that natural seawater is 1.022 /1.023 comes from.

I think it was Boomer who years ago suggested that some of the early aquarists apparently confused the density of seawater with the sg. The density of 35 ppt seawater at 81 deg F is 1.0226 g/cm3.

[CHSUB]

Just looking for a few comments on this subject. I been doing reefs for quite a few years but just coming back from a long hiatus from the hobby.

For many years I ran tanks at 1.022 sg. Typical reef tanks with a large mix of LPS, softies, anemones, inverts and fish and never had a problem. In fact in the case of an ich outbreak a little higher heat and slightly lower SG where always good for a cook off of disease with no detrimental effects to the tank. The higher the SG the more some diseases like ick thrive. Generally speaking 1.022 was the norm (natural seawater ~1.022-1.023) and no one ventured past 1.024.

So I'm a little perplexed with all the people especially new comers running SG of 1.025. I see it mentioned all the time and in sigs. I can maybe see that with the proliferation of people doing (or trying to) SPS but when did a high SG like that become the "norm" and what's the reasoning. I would have to think that SG, at minimum, increases the fish mortality rate.

it was common in the late 90's to run sg lower than NSW. i did for many years without ill effects. LFS still do today (maybe to save on salt), however, most hobbiest today have moved closer to NSW's sg.

[Randy Holmes-Farley]

I don't know where the idea that natural seawater is 1.022 /1.023 comes from.

I think it was Boomer who years ago suggested that some of the early aquarists apparently confused the density of seawater with the sg. The density of 35 ppt seawater at 81 deg F is 1.0226 g/cm3.

Here's an example where Albert Thiel screwed it up (original book came out in 1988):

http://www.netpets.com/fish/reference/thielbook/thielbook8f.html#8.12

from it:

"Many hobbyists measure the specific gravity rather than the salinity. The specific gravity (s.g.) that I suggest, which corresponds to 35 ppt salinity, is 1.0234 at 77 Degrees Fahrenheit. "

Totaly untrue. The density of 35 ppt seawater at 77 deg F (25 deg C) is 1.0233 g/cm3

which is from:

http://www.es.flinders.edu.au/~mattom/Utilities/density.html


The density of pure fresh water at that same temperature is 0.997047 g/cm3,

which is from:

http://antoine.frostburg.edu/chem/senese/javascript/water-density.html

giving a sg of 1.0233/0.9970479 = 1.0263. :)

[tmz]

Thankyou Randy. It clears it up nicely.

[CHSUB]

Here's an example where Albert Thiel screwed it up (original book came out in 1988):

http://www.netpets.com/fish/reference/thielbook/thielbook8f.html#8.12

from it:

"Many hobbyists measure the specific gravity rather than the salinity. The specific gravity (s.g.) that I suggest, which corresponds to 35 ppt salinity, is 1.0234 at 77 Degrees Fahrenheit. "

Totaly untrue. The density of 35 ppt seawater at 77 deg F (25 deg C) is 1.0233 g/cm3

which is from:

http://www.es.flinders.edu.au/~mattom/Utilities/density.html


The density of pure fresh water at that same temperature is 0.997047 g/cm3,

which is from:

http://antoine.frostburg.edu/chem/senese/javascript/water-density.html

giving a sg of 1.0233/0.9970479 = 1.0263. :)

maybe this was the reason at the Harvard Lab, but not at the LFS! we had a swing arm hydrometer and kept sg lower for a number of reasons, many false; but it had nothing to do with confusion about density.

[bertoni]

I think it was Boomer who years ago suggested that some of the early aquarists apparently confused the density of seawater with the sg. The density of 35 ppt seawater at 81 deg F is 1.0226 g/cm3.
That's interesting. Maybe that's what happened.

[zoomonster]

Thanks for the feedback... was curious how it all evolved and misinformation seems key although never had a problem at 1.022 including the early days where I manually added topoff water and it fluctuated quite a bit. I know, especially in 90's, a lot of shops ran pretty low sg in fish holding tanks. More than one shop owner said it was to help control disease. Whether misinformed or not that's what they did.

[Randy Holmes-Farley]

If you believe random anecdotes, some creatures, like some of the carpet anemones, do better at higher salinity. Not as many of those were kept successfully in the 90's. :)