What is Your Specific Gravity?

[mfsolecki]

TEMP

= 75F night - 78Fday (due to lighting: nothing seems to mind the diurnal flex -- I'm a marine phyicist -- real world can be > 6F shift...even @ >60'-- depending on location, time of yr, cloud cover type and length of time, as well as tubidity (amount and material), most of which determines macro-evap rate-----these critters are pretty hardy to physical changes, chemical changes (including ionic) are more serious (stable is a key word here) -- Of course the mix of what you have in your tank will also affect the ecology and the chemical tolerances to each others influences -- since you're creating a micro-env and each critter metabolizes things differently -- so, I think temp is a minor influence as long as it is kept w/in a range and if the circulation and the SG/Sal has to be "stable" reguardless of what is optimal)...OH! I try to keep it at 1.023 (sorry)...I guess I should have mentioned that I use a "Deep Six" meter and it has a 68-85F calibration range but how technical do you want to get -- my critters seem HAPPY! and I guess that's what matters.....

 

[NaH2O]

Welcome to REEF FRONTIERS!!!

 

[cubera]

spgr

1.024 @80 SPS
1.021@78 LPS

 

[edgekrusher]

Temp stays at a constan 81.5 degrees.

 

[NaH2O]

EK - Welcome to Reef Frontiers!!! Nice to see you here! What do you keep your specific gravity at with the temp of 81.5F?

 

[edgekrusher]

My refractometer reads 1.024.

 

[Beeba]

1.025 @ 80-82 Seems I can't get my temp under 80 in the summer.

 

[mojoreef]

Man...you guys are using salt???? ....dammm


Mike

 

[mfsolecki]

Beeba--that is allot of salt...is that intended???? or due to evap w/the high temp???? try raising your lights higher above your tank or a small computer fan (Radioshack sells them pretty cheap) accross the top....

 

[Beeba]

I can put the legs on my light fixture to raise it up a bit. I never use saltwater to top off so that should take care of the evaporation issue. Everything in the tank seems happy at this level. Any signs of problems that I should look for?

 

[Hooked]

I guess I'm missing something. 1.025 is fine Beeba

 

[Beeba]

I thought it was. That is what mojo told me I should have. I know I should have the temp around 78-80 but everything seems fine with where it is.

 

[reeffan]

1.026 with 80-82 degrees during hot days....man i need a chiller =).

reeffan

 

[NaH2O]

1.025 @ 80-82 Seems I can't get my temp under 80 in the summer.

Beeba, just a bit of information for you. If you are reading your specific gravity at 1.025 on a refractometer, then that value is actually 1.024 (~33ppt?). The majority of refractometers are calibrated to salinity of NaCl, which is different than NSW. A 35ppt refractive index on NaCl is not equal to a 35 ppt refractive index for sea water. In order to compensate for the 0.001 difference (which it is when it leaves the store)..... a specific gravity on a refractometer reading 1.027 at any normal temperature (since most refracts are ATC) = 1.026 (corrected SG) = 35 ppt.

Shouldn't we be trying to achieve correct salinities in stead of specific gravity? We base our chemistry on salinity.

 

[Curtswearing]

Good point.

Natural Sea Water (NSW) is 35 ppt. I like to mimic my corals natural habitat so I run 1.025 to 1.026 at 79 to 80 degrees to get to 35ppt. The conversion from 35ppt to SG can be seen on the attached pic from Nikki's link. It's my understanding that Habib (Salifert) calibrates many of his reagents to a specific gravity of 1.025. When people post that their test kit is WAY OFF, he often asks what their salinity or specific gravity is because this has tremendous impact on the readings.

I don't know what salinity the other manufacturers calibrate to but it seems to me that it would be NSW. I wonder how much our test results are off if we are running at a lower specific gravity than our test kits are calibrated for.

Now that's a beautiful bell curve

LOL!!!

 

[J McCauley]

Have FO only system and I run it at 1.018 @ 78

 

[fishermann]

curtswearing Have you checked you float arm meter against a refractmeter? my float arm reads 1.024 when my refracto says it is 1.025. I had a red sea float arm that was .002 off. You should have someone with a refracto check you arm meter for accuracy.

 

[Curtswearing]

Comparing with a refractometer is a very good practice. Good post!!! Salts can build up on the swing arms over time and give false readings.

I use both swing arms and a refractometer. I use a refractometer whenever I do a waterchange. However, since I've switched to running my skimmer very wet, I periodically want to doublecheck my SG very quickly and use a Sea-Test or Corallife Deep Six swing arm for these purposes.

Just to confuse matters a little more, the .001 difference doesn't mean that your swing arm was wrong. Actually, it means your swing arm was right as refractometers read .001 (actually .0015) too high due to being calibrated with NaCl instead of NSW. This is not a failure of a refractometer as they will give you consistent readings. Swing arms will not give you a consistent reading unless they are rinsed with RO/DI water after every use and soaked in vinegar once per month. I have recently read that they should also be stored in zip-lock bags in between uses.

If you want 35ppt, here's how you get there.

Refract 35 ppt NSW Salinity = 1.027 SG ATC
If it is a Seatest or Swing Arm type 35 ppt Salinity NSW = 1.026 at any normal temperature

 

[NeilsReef]

1.024 @ 78 degrees

Normally it is like this.

 

[class clown]

1.024 & 77.5 degrees