Specific Gravity::What SG level do you target and why??

Discussion in 'Water Chemistry' started by NASAGeek, Jan 18, 2010.

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What SG level do you target?

Poll closed Feb 1, 2010.
  1. <1.020

    0 vote(s)
  2. 1.020-1.021

    0 vote(s)
  3. 1.022-1.023

  4. 1.024-1.025

  5. 1.026

  6. > 1.026

    0 vote(s)
  1. NASAGeek

    NASAGeek Eyelash Blennie

    Nov 16, 2009
    Houston, TX
    Specific Gravity (SG)
    -LiveAquaria.com Suggested Reef Aquarium 1.023 - 1.025
    -ReefKeeping.com Suggested Reef Aquarium 1.026
    -LiveAquaria.com Suggested FOWLR Aquarium 1.020 - 1.025
    -Natural Reef 1.025-1.026

    Poll Question:
    What SG level do you target and why??

    Second question: If you measure your SG and it is too low or too high, what procedure do you use to adjust it?

    If too low, suggest doing what?.... How? add salt to sump or Water change with higher salinity water? How do you determine how much salt to add?

    If SG too high, suggest doing what?.... water change and adding RO/DI instead of salt water?? How do you to determine how much water to remove and how much RO/DI to replace?

    If mine is low, I have been adding small amounts of salt to my sump every few hours to gradually raise it. Roughly 1/2 cup per hour for a 75 gal total water volume system until 1.024 is reached.

    If it is too high, I take some water out and replace with RO/DI every few hours to gradually reduce it. Roughly 1/2 gal salt water removed and 1/2 gal RO/DI replaced every hour for a 75 gal total water volume system until 1.024 is reached.

    Final question:
    I use a refractometer to measure salinity. Hydrometer based SG measurement are too imprecise for these measurements based on my research. Alternative would be a digital probe of some kind at additional expense.

    Any better ways of doing this??
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  3. Night-Rida

    Night-Rida Finback Whale

    Jul 3, 2009
    Tampa, FL
    1.025 high salinity can hold more mag, & cal, etc.. saltier water holds more..

    if low, and dont need water change. I just make up a real salty 1gallon bucket of new topoff water to add to sump

    if high, take 1 gallon out of tank.. and add 1 gallon of fresh non-salted water.

    I have two hydrometers and they are off from each other my .022.. so 1 reads 1.025 other reads 1.027.. :) I had to take it to the LFS to test it with theirs.. so I know which one works right.. also different water temps give different readings..
  4. ZachB

    ZachB Giant Squid

    Oct 12, 2008
    1.025-1.026 - nsw
  5. steve wright

    steve wright Super Moderator Staff Member

    Feb 17, 2009
    shenzhen Guangdong PRC
    target 1.025 myself for same reason as Zach B - is an oft quoted figure for Natural Sea Water (never measured in the sea though to be honest so Im taking lots of other peoples word for this and some of them must have measured the sea at some point LOL)

    I do 5% weekly water changes and try to get my SG to the same level as I have in my tank- so to be honest I never had much SG fluctuation in my tank (although irrespective of how many times I make SW in the 5 gallon bucket I always seem to be a little to low or to high after 24 hours so in the bucket I may add salt or add RODI)

    if my SG was at 1.024 - 1.026 then I would be happy and do nothing to change this
    if my reef tank SG was to low, below 1.024 then I would add SW at top off thus the salinty would slowly increase as I would be compensating for lost FW with SW

    if my SG was to high ( for example I had been using a needle pointer hydrometer and later used a refractometer and found out my needle pointer was reading to low)
    well under these circumstances - if everything looked OK in the tank I would just mix my water change water to 1.026 and bring it down gradually over a period of a few weeks

    with a new set up, without any live stock in- then Id make an abrupt change taking SW out and adding RODI water in

    I am of the opinion that you should not raise or reduce your SG by more than 1 point per day (according to what I read and learned about hypo salinity treatment in DTs for parasites)
    so if you had 1.030 and wanted 1.026 - then you should take 4 days over bringing it down at least and as stated above, if everything in the tank has become gradually accustomed to that level, then gradually bringing it down is ideal IMO

  6. szrazzt

    szrazzt Purple Spiny Lobster

    Nov 28, 2008
    I dont sweat the SG too much, I just try to keep it at about 1.025. If it looks low i will make SW that is a bit too salty during my water change which happens every couple weeks. If it is a bit high it is normally because I havent added top off water in a few days and the sumps water level is low. When that happens I add RO water every day until it gets back to where it is supposed to be.

    Its really easy to get behind on top offs with a 55 gallon sump and only loosing 1 gallon for evaporation per day.
  7. =Jwin=

    =Jwin= Tassled File Fish

    Nov 26, 2008
    Chattanooga, Tennessee
    Our reef tank is about 1.024 to 1.025 depending on its mood :) Normally it's stable at 1.024.

    To raise salinity, just top off with salt water instead of fresh water until it reaches what you want. It'll take a few days, but that's a good thing.

    To decrease it, take a gallon or similar measurement (depending on tank size) and add a gallon of fresh. For our tank which is a 46, I'd probably do half gallon increments. And then if you have a nano aquarium, obviously you don't want to take out a gallon and add a gallon of fresh water. For a nano, I'd probably incorporate some trick to lower it through water changes. Maybe low salinity water (1.021 or something) and let it decrease that way.

    Also, I feel that some hydrometers can be trusted, as long as they are calibrated to a refractometer or similar. I remember when we took our hydrometer to the LFS, it actually showed them that their frag tanks were at 1.0235 which is not where they wanted them to be at. You go, little hydrometer you. :)
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  9. lunatik_69

    lunatik_69 Giant Squid

    Jul 10, 2007
    Miami, FL

    This is also my target level.

  10. Screwtape

    Screwtape Tonozukai Fairy Wrasse

    Sep 25, 2008
    I target 1.025 since it gives a little bit of leeway before going too far out of the range I'm aiming for which is 1.024 to 1.026. AFAIK most coral will handle this range well and going outside of that can have some issues (at least with some corals).

    Also AFAIK 1.026 is some sort of average or maybe the most common salinity found on natural reefs. There are areas of higher or lower salinity, the red sea is higher salinity, for example, from what I've read.

    As for raising/lowering salinity, if I need to raise it I just top off with saltwater basically. If I need to lower salinity I just remove a small portion of water from the tank and let the ATO replace it with RO water when it gets around to it. I also try not to change my salinity too drastically, 1 point a day max, preferably not all at once as well but removing/adding small portions of water several times over the course of the day.
  11. stylaster

    stylaster Gigas Clam

    Dec 18, 2007
    Kelso, WA
    mine is between 1.025 and 1.026
  12. baugherb

    baugherb Giant Squid

    Sep 8, 2007
    southington, ohio