The Debate Thread....

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spacepony

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So, I think the title says it all...

I note the true desire for many-a-hobby-lover to THOROUGHLY discuss (read 'bash a dead horse until he's mush') countless debatable and germane topics on all things marine. I have high hopes that perhaps this could become a dutiful arena for all major opinions . . . .:)

SO, in true SNL '"Cawfee Tawk" with Paul Bawldwin' fashion, I throw out a starting topic here (of recent interest...):

Hyposalinity: Miracle or Myth?

"Talk Amongst Yourselves"
 
I wanted to get my two cents in (mostly thought and speculation more than opinion) without disrupting a previous thread where this had become the ad hoc topic. (I also do hope this thread gets used frequently for such discussion as wanders outside an op's intyended topic).
So, on salinity: Noting from an old Oceanography book (Essentials of Oceanography by Thurman) that the ocean is not precisely ONE salinity, that in fact it will vary between 34ppt to roughly 36.7ppt (roughly 1.026 to 1.028) in the upper 500m of water (more variation at the surface), and also noting by common observation that the margins of oceans are constantly beset with river inflow, and heavy rain, I wonder what the ACTUAL salinity values in surface waters actually are? How low do they go? And by extension, when does it start affecting marine life?
 
coolsurf;534080 wrote: Good opening topic....

What relationship to? Permanent or treatment?
Click to expand...

Shrimpy Brains;534082 wrote: Are you meaning hyposalinity used to combat ich??
Click to expand...

Well, as treatment, I think it has been shown to be often effective. I am refering mostly to the debate that started on whether keeping fish at 'hyposaline' levels is harmful or benficial to the actual overall health of the fish.
 
I'll stick my neck out here, and say that the optimum SG for the health of the fish (with no other considerations) is that of NSW. There is no way a fish could evolve in nature to a salinity other than that... it would adapt to its environment, not away from it. And, among captive bred fish, there could be no significant evolution or long term adaptation in the short time we have been holding these fishes in captivity.

I'm not a marine biologist, and don't claim to be, but to me this is common sense.
Bring parasite control into the discussion and that changes things somewhat... it might be an imperfect environment for the fish, but if it can keep them "clean" then it's a worthy tradeoff.
 
Personally I keep mine as close to 1.024 as I possibly can. I know that evaporation will raise the salinity throughout the day so I try to compensate a bit. I also want room for leway. The fish are not stressed nor are the corals and the inverts seem fine so I run with it as long as it works. In real life, the seas vary. One part of the ocean is 1.027 and another at 1.025. Consistancy is not there.

As for the effects on a fish, fish work at getting rid of salt naturally so does hypo help? Maybe.
 
spacepony;534083 wrote: I wanted to get my two cents in (mostly thought and speculation more than opinion) without disrupting a previous thread where this had become the ad hoc topic. (I also do hope this thread gets used frequently for such discussion as wanders outside an op's intyended topic).
So, on salinity: Noting from an old Oceanography book (Essentials of Oceanography by Thurman) that the ocean is not precisely ONE salinity, that in fact it will vary between 34ppt to roughly 36.7ppt (roughly 1.026 to 1.028) in the upper 500m of water (more variation at the surface), and also noting by common observation that the margins of oceans are constantly beset with river inflow, and heavy rain, I wonder what the ACTUAL salinity values in surface waters actually are? How low do they go? And by extension, when does it start affecting marine life?
Click to expand...

Ok, based on the above statement, I guess it would matter based on what particular marine life we are talking about.
There are some that prefer to live in the "lower salinities" where the rivers run to the sea. Some will even swim up the river into completely freshwater.
However, there are many that cannot tolerate lowered salinities and will die!
The problem with using this as a reference for keeping a reef tank is, there are very few reef tanks that only house specific critters from specific areas. Most reef systems are diverse by design. What you have to do is find the best compromise for all the critters in your particular system.

I would also say it depends on what you define as "hyposaline". Are we talking. 1.021 or 1.009 or what point do you find is the dividing line?
 
cr500_af;534089 wrote: I'll stick my neck out here, and say that the optimum SG for the health of the fish (with no other considerations) is that of NSW. There is no way a fish could evolve in nature to a salinity other than that... it would adapt to its environment, not away from it. And, among captive bred fish, there could be no significant evolution or long term adaptation in the short time we have been holding these fishes in captivity.
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Agreed, but what about the change in sea salinity over time? I'm wandering out on a limb here, because I can't immediately find hard data about how MUCH it changes, but I am running across several statements on how the oceans get more or less saline based on major climate cycles (i.e ice ages, warmings)..

Shrimpy Brains;534092 wrote:
I would also say it depends on what you define as "hyposaline". Are we talking. 1.021 or 1.009 or what point do you find is the dividing line?
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Yes. And that is another point. I'm seeing different versions of what defines 'hyposaline' seeing as how NSW is variable.
 
I know it's possible to acclimate a fresh or brackish fish to sea water but are there any salt water fish that can be acclimated to fresh or brackish water.

Also, it seams reasonable that, if the ocean has varying salinity any mobile creatures can move to where it is more comfortable for them. In our tanks, the fish have no choice but to endure, adapt, or die.:sad:
 
moebious;534116 wrote: I know it's possible to acclimate a fresh or brackish fish to sea water but are there any salt water fish that can be acclimated to fresh or brackish water.
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FYI...
a>
 
And to peak your interest even more.....http://www.aquariumlife.com.au/showthread.php?14122-The-next-evolution-in-fishkeeping..Gex-magical-water">http://www.aquariumlife.com.au/showthread.php?14122-The-next-evolution-in-fishkeeping..Gex-magical-water</a>

Sorry about the b2b post
 
spacepony;534105 wrote: Agreed, but what about the change in sea salinity over time? I'm wandering out on a limb here, because I can't immediately find hard data about how MUCH it changes, but I am running across several statements on how the oceans get more or less saline based on major climate cycles (i.e ice ages, warmings)..
Click to expand...

My take on that is this: we're talking about optimum conditions, and the variations over time tell us that the fish can survive and reproduce in less than optimum conditions. I guess until we get an Apex on the ocean and start keeping birth/death certificates on fish we'll never know! :lol2:
 
Yeah that's really scary...

FWIW, I never suggested that it's bad practice to keep a reef aquarium at 1.026. In the context in which the discussion began, I wondered if the death of a fish introduced to a tank with that SG, may have suffered osmotic shock *if* it came from a lower specific gravity.

In that instance, the hobbyist did not know the specific gravity that the fish came from - so if there's one good thing to come of that discussion, it would be a wise idea for people to check the SG of bag water versus their own water, and adjust their acclimation procedures accordingly if there's a gap either way (higher or lower).

I'd also submit that it's not good enough to ask the store or whatnot, what their SG is. Test it, and test one's own with the same tester. If 2 samples are tested with 2 different devices, there's also a possibility that one isn't calibrated the same as the other. So if 2 samples are tested with the same device (ie bag water and tank water), the individual will know if there's a difference and how much of a difference there is.

I keep my SG at 1.023-1.024 in reef systems, and 1.022-1.023 in FO systems.

The pre-made water I sell, I target 1.023-1.024.

Plenty keep it higher, like I said, I don't think that's a bad thing, IMO it's not an "exact science" and there is an acceptable range, not one precise number. Consistency is more important, IMO.

In my experience, many wholesalers keep their SG in the same range I do, so that makes it easier to acclimate new arrivals - less stress/changes for them.

Other sellers recommend similar ranges also...

http://www.fosterandsmithaquatics.com/pic/article.cfm?aid=1304">http://www.fosterandsmithaquatics.com/pic/article.cfm?aid=1304</a>

[IMG]http://www.aquabuys.com/c/nano-reef-aquarium.html">http://www.aquabuys.com/c/nano-reef-aquarium.html</a>

(Scroll down about 1/4 of the way down the page for the chart)

[IMG]http://kb.marinedepot.com/article.aspx?id=10252">http://kb.marinedepot.com/article.aspx?id=10252</a>

About 1/3 down the page:

[QUOTE=]By using a hydrometer or a refractometer you are able to find out how much salt is in the water. Ideally most saltwater tank will run best with a specific gravity of 1.020 to 1.025 or a specific gravity of 26-33 ppt with most keeping the specific gravity closer to the 1.025 range.[/QUOTE]


RHF acknowledges that reef aquaria can run just fine at 1.023, although his recommendation is higher at 1.026. He does seem to believe that people don't measure accurately though :-/

[IMG]http://reefkeeping.com/issues/2007-03/rhf/index.php#1">http://reefkeeping.com/issues/2007-03/rhf/index.php#1</a>

[QUOTE=]Fortunately, coral reef aquaria seem rather forgiving with respect to salinity. The range of salinities encountered in what most would proclaim as successful reef aquaria is actually quite large. Don’t agonize over small deviations from natural seawater. You will not notice any benefit changing from 36 or 34 ppt to 35 ppt (specific gravity = 1.0256 to 1.0271).[B] Many fine reef aquaria appear to run at salinity levels as low as 31 ppt (specific gravity = 1.023), but bear in mind that the values that aquarists report (as well as your own measurements) are fairly likely to be inaccurate, so pushing the low or high end of the range may not be prudent.[/B] [/QUOTE]


So while we might disagree with what "ideal" is, I think these examples demonstrate that there is a fair range of what is "acceptable".

Apparently the question has been going around for a while, I found this old poll from 2001 (RHF contributed to it also)...

[IMG]http://www.reefland.com/forum/reef-archives/4990-what-your-ideal-specific-gravity.html">http://www.reefland.com/forum/reef-archives/4990-what-your-ideal-specific-gravity.html</a>

While 1.025-1.026 got just over 53% of the votes, 1.023-1.024 came in second with just over 38% of the votes.

Jenn
 
I'm inclined to believe, considering there are freshwater tributaries pouring in the ocean that there is great varience in the salinity of the ocean. I guess it depends on where you define the ocean starts and rivers end etc. Also considering fish like Zambezi sharks I am enclined to believe acclimation goes both ways in a lot of species. I guess that would have a lot to do with the fishes capability of handling osmotic pressure changes. One thing I have learned is that fish are able to adjust to lower salinty faster than higher salinty. This is one of the key reasons for dripping a fish because a lot of supplier run at lower salinity.

As far as the hypo, it seems to work. However it seems key to hit the 1.009 mark. The parasite cannot acclimate to the lower salinity like the fish. It will also kill inverts such as snails etc. As far as long term effects on the fish I couldn't tell you but it might depend on the fish also.
 
Here's a very interesting article on the benefits of hyposalinity.

http://www.advancedaquarist.com/2006/3/aafeature1">http://www.advancedaquarist.com/2006/3/aafeature1</a>

Jenn
 
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