ok hyposalinity question

[mummra100769]

will hyposalinity cause fish to die?what about prolonged use of hyposalinity?what is the bad side to hyposalinity?help randy!

[JoeMack]

You need to lower the salinity slowly. Its more easy on the fish in the a hypo solution becides its kidneys. The water is more closer to the fishes body in the hypo and the fish doesnt have to push as much water through its body....

Here is a snip from this page
http://www.reefkeeping.com/issues/2003-08/sp/

"Reef fish have to constantly drink saltwater and excrete the salt to maintain the proper osmotic balance. Lowering the salinity of the surrounding environment eases this energy demand on the sick fish, thereby allowing them to expend more energy towards fighting the infection (Kollman, 1998 and Bartelme, 2001). On the contrary, keeping fish in low salinity means that they don't "flush" their kidneys sufficiently. After long-term exposure, this can cause kidney failure and kill the fish (Shimek, pers. comm..)"

[Randy Holmes-Farley]

will hyposalinity cause fish to die?

Are you talking about short exposures, or permanent situations?

[Boomer]

On the contrary, keeping fish in low salinity means that they don't "flush" their kidneys sufficiently. After long-term exposure, this can cause kidney failure and kill the fish (Shimek, pers. comm..)"

Hmm, what about those fish that can live in either environment. So, this is not totally correct. Example; the Marine Lamprey Petromyzon marinus, Steelhead/Rainbow Trout Oncorhynchus mykiss, Atllanic Salmon Salmon salar and the Chinook salmon Oncorhynchus tshawytscha all live in both the ocean and Lake Superior. To include other species of fish in lake Superior, Ruff Fish, Coho Salmon, Pink Salmon etc.. There are many other examples to include a number of FW fish that can adapt to seawater and vice-versa. However, it may be an issue for reef fish in general.

[mummra100769]

long term is what i meant.what are the long term affects of hyposalinity.if there are none why dont we run hypo all the time?

[Randy Holmes-Farley]

Because it isn't optimal for reef inhabitants.

I'd suggest reading this article:

http://web.archive.org/web/20010606095357/http://www.animalnetwork.com/fish2/aqfm/1997/nov/features/1/default.asp


From this article:

Reef Aquarium Water Parameters (a summary general article)
http://www.reefkeeping.com/issues/2004-05/rhf/index.htm

"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)."

[Randy Holmes-Farley]

Here's an example of an article from the scientific literature showing that sea urchins do not do as well in hyposaline water:

Effects of salinity on respiration and nitrogen excretion in two species of echinoderms. Sabourin, T. D.; Stickle, W. B. Zool. Physiol. Dep., Louisiana State Univ., Baton Rouge, LA, USA. Marine Biology (Berlin, Germany) (1981), 65(1), 91-9.
Abstract

The 30-day survival limit of Eupentacta quinquesemita and Strongylocentrotus droebachiensis is 12-30.permill. salinity. The activity coeff. (1000/righting time in seconds) of stepwise acclimated sea urchins declined from 16.3 at 30.permill. salinity to 3.5 at 15.permill. salinity. O consumption rates (Q) of both species held at 30.permill. salinity and 13° were highest in June and lowest in Dec. During the summer, when environmental salinity is most variable in southeastern Alaska, the Q of both species held at 30, 20, and 15.permill. salinity varied directly with salinity. Perivisceral fluid pO2 varied directly with acclimation salinity in sea urchins, but not in sea cucumbers. Perivisceral fluid O content of acclimated sea urchins was significantly lower at 15 and 20.permill. salinity than at 30.permill. salinity due to reduced pO2 and extracellular fluid vol. at the lower salinities. The Q of both species varied directly with ambient salinity during a 30-10-30.permill. semidiurnal pattern of fluctuating salinity. Sea urchin perivisceral fluid pO2 declined as ambient salinity fluctuated away from the acclimation salinity in both cycles and increased as ambient salinity returned to the acclimation salinity. Total N excretion of stepwise acclimated sea cucumbers declined significantly from 30 to 15.permill. salinity, but there was no salinity effect on total N excretion in sea urchins. NH3 excretion varied directly with salinity in stepwise acclimated sea cucumbers (67-96% of total N excreted), but there was no salinity effect on NH3 excretion (89-95% of total N excreted) of sea urchins. Primary amines varied inversely with salinity in sea cucumbers (2-30% of total N excreted), but did not vary with salinity in sea urchins (2-4% of total N excreted).

[mummra100769]

thank you for all the great info.one more thing,what about fish only set ups?do these rules still apply.once again thanx