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Old 02-02-2005, 08:35 PM   #1
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Specific Gravity

My temp is currently 55 degrees. I am waiting for my heaters to heat the water up. Do I have to wait until the temp reaches about 77 before I can add salt and use my hydrometer or can I trust that the temperature difference will be minimal?

Does anyone know what corresponds to a 1.023 SG at 55 degrees? Thanks!

JW
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Old 02-02-2005, 09:01 PM   #2
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whats the hurry...... Wait or add some salt and wait till the temp is up before you make the final adjustment.
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Old 02-02-2005, 09:07 PM   #3
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I've got livestock, live rock, and live sand waiting to go back into the tank. (My tank broke so now I'm setting up a new one, thus the low temp.) That's why I want to get teh salinity up to par asap. I guess it doesn't matter though, cuz I shouldnt even add the LS until the temp is normal.

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1 Yellow Tang
1 Mandarin Goby
3 Peppermint Shrimp
20 Red-Legged Hermit Crabs
30 assorted Snails

6G Nano-Reef Tank (Eclipse Six)
--------------------------------------------
10 lbs. LR
15 lbs. LS
1 Sebae Anemone
Several Purple Mushrooms
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1 Sebae Clownfish
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Old 02-02-2005, 09:30 PM   #4
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Depends on the kind of hydrometer you are using and how it was calibrated.
Plastic swing arm types won't have a great variation but proper glass floating hydrometers are calibrated at a specific temp and must have a conversion factor applied, depending on the temperature spread.
Swing arm type need to be checked for accuracy against a certified hydrometer or a refractometer.
I have a certified hydrometer from Fisher Scientific and it was calibrated at 60F and to accurately measure my salt water I have to adjust by ,0028 for my 80F water.
I keep all my tanks at 80F and I keep my specific gravity at 1.026 which is what the reefs are normally at.
I mix my water up with more salt than needed for my desired level and then add more water after it has fully mixed, to bring it up to that level.
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Old 02-02-2005, 09:32 PM   #5
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Quote:
Does anyone know what corresponds to a 1.023 SG at 55 degrees? Thanks!
The density of water changes at different tempeatures. Since specific gravity is a ratio of water to something else, this has a pretty big impact.

Your measurment of 1.023 SG at 55 degrees will be quite different when you measure again at 78 degrees.
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Old 02-02-2005, 09:44 PM   #6
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So, according to rayjay, the SG difference between 60F and 80F is only 0.0028? This means that I can pretty accurately get my salinity to measure 1.024 at 60F and I will, once the temp reaches 80F, have an SG of 1.0268. So I should shoot for an SG at 60F of about 1.022? Does this all sound right?

JW
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55G Reef Tank
-------------------------------------------
80 lbs. LR
40 lbs. LS
1 Pink Tree Coral
1 Copperband Butterfly
1 Yellow Tang
1 Mandarin Goby
3 Peppermint Shrimp
20 Red-Legged Hermit Crabs
30 assorted Snails

6G Nano-Reef Tank (Eclipse Six)
--------------------------------------------
10 lbs. LR
15 lbs. LS
1 Sebae Anemone
Several Purple Mushrooms
1 Bright Green Brain Coral
1 Sebae Clownfish
1 Yellow-tailed Damsel
1 Domino Damsel
6 Red-Legged Hermit Crabs
8 assorted Snails
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Old 02-03-2005, 03:06 AM   #7
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You still didn't mention anything about your hydrometer.
That question can't be answered without knowing how your hydrometer was calibrated.
If you use the plastic swing arm, it won't make a great deal of difference as they seem to work well at quite a large range, at least for the range normally used in the hobby. However they are not known for their accuracy right from the start so they need to be calibrated against a known calibrated standard first. They also need to be rinsed after each use, and, cleaned approx. weekly in white vinegar overnight.
If it is a glass floating hydrometer, you need to know what temperature it was calibrated at so appropriate adjustments can be added. If you look at the paper inside the tube, there should be information to this effect printed on that paper.
If it is not a certified hydrometer, again, it should be checked against a known calibrated standard before depending on it.
If it is a hydrometer sold specifically for the hobby, it is generally calibrated for temperatures normally found in the reef hobby, but again, the accuracy can be suspect until compared to a standard.
Also, for accuracy, the glass floating hydrometers should not be used in the aquarium, but the water should be transfered to a cyclinder where there is no water movement to create a false reading on the hydrometer.
I clean mine on a regular basis, again, with white vinegar, to keep proper calibration.
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Old 02-03-2005, 10:52 AM   #8
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It is a swinging arm hydrometer. I got it up to like 1.022 @ 65 - 70 degrees F and now it's up to 79F and the SG is 1.023, which is how I like it. Thanks for all your help everyone!

JW
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55G Reef Tank
-------------------------------------------
80 lbs. LR
40 lbs. LS
1 Pink Tree Coral
1 Copperband Butterfly
1 Yellow Tang
1 Mandarin Goby
3 Peppermint Shrimp
20 Red-Legged Hermit Crabs
30 assorted Snails

6G Nano-Reef Tank (Eclipse Six)
--------------------------------------------
10 lbs. LR
15 lbs. LS
1 Sebae Anemone
Several Purple Mushrooms
1 Bright Green Brain Coral
1 Sebae Clownfish
1 Yellow-tailed Damsel
1 Domino Damsel
6 Red-Legged Hermit Crabs
8 assorted Snails
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Old 02-03-2005, 12:53 PM   #9
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FYi, you might wanna look into a refractometer...temperature doesn't matter, no bubbles to dislodge, and you can re-calibrate it in 15 seconds as long as you have some distilled water or RO on hand.
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Old 02-04-2005, 12:33 AM   #10
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Quote:
and the SG is 1.023, which is how I like it
Is this for a fish only tank? Just curious as to why you like the specific gravity so low.
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