Specific Gravity

[Ase@]

I have a 8 gallon IM Nuvo reef tank. I live in Las Vegas. My tank has been up over a year. I have kept parameters in check, done weekly water changes ( One gallon). I am, and have been, running filter floss, chemi-pure, and purigen, in my filter area. Since the colder weather, I have found that my S.G. seems to be increasing and is now running at 1.065. Things have never looked better in my tank!!! &nbsp;I have a large green toadstool mushroom leather, green &amp; blue colony zooanthid, candy cane coral (just divided), favia coral, pulsing zenia, montipora (has been growing nicely). I also added a peppermint shrimp. NO FISH! &nbsp;It seems as the S.G. goes up, the corals do better! &nbsp;Any advice???? &nbsp;I don't have any RODI trickler, but I do add RODI as needed.<img src="https://www.reef2reef.com/forums/images/smilies/cutemoticons/cutemoticons/cry.png" border="0" alt="" title="Cry" smilieid="379" class="inlineimg"><img src="https://www.reef2reef.com/forums/images/smilies/cutemoticons/cutemoticons/wink.png" border="0" alt="" title="Wink" smilieid="388" class="inlineimg"><img src="https://www.reef2reef.com/forums/images/smilies/smileR2R/thumb.gif" border="0" alt="" title="Thumb" smilieid="592" class="inlineimg"><br>.

 

[brandon429]

is that from refractometer or swingarm?

 

[Ase@]

Instant Ocean Swingarm

 

[Randy Holmes-Farley]

Since the colder weather, I have found that my S.G. seems to be increasing and is now running at 1.065. Things have never looked better in my tank!!! .

I presume you mean 1.0265? 1.065 is unbelievably saline and should not yield thriving corals.

The ocean average of 35 ppt is about sg = 1.0264, so you are right on target, IMO.

 

[Ase@]

My bad, I DID mean 1.0265

 

[Randy Holmes-Farley]

How low was it previously?

I always recommend 35 ppt as an appropriate goal for reef aquaria:

https://www.reef2reef.com/forums/re...-coral-reef-aquarium-randy-holmes-farley.html

from it:

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 has no units) 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 an average salinity of about 35 ppt, corresponding to a specific gravity of about 1.0264 and a conductivity of 53 mS/cm. It often ranges from 34-36 ppt over reefs, but can be higher or lower locally for various reasons such as land run off of fresh water, or evaporation from a lagoon.


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. I have no idea if that is true or not, but I’ve not seen evidence that it is true. Substantial misunderstandings have also arisen in the past among aquarists as to how specific gravity really relates to salinity and density, especially considering temperature effects. For example, the density of seawater is less than the specific gravity, and measurements with glass hydrometers may require temperature correction, but newer devices do not need the aquarist to make corrections. Consequently, older salinity or “specific gravity” recommendations may not actually be referring to the same measurements that aquarists make today, even if the recommended numbers have been handed down


My recommendation 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 target salinity of 35 ppt (specific gravity = 1.0264; conductivity = 53 mS/cm).

 

[Ase@]

S.G.

I have tried to keep it at 34. It has gone as high as 38 with no noticeable effects on the corals. The fluctuation started as the colder weather started, and the heater kicked in, causing evaporation of course. I didn't see the need to spend a lot of money on a hydrofil pump since I don't have the money to spend. I usually add some rodi water to my sump as I feel it's needed to keep the S.G. in check.