Specific Gravity

[cbianco]

Ok so I haven't checked the specific gravity in my tank for some time now. I got in the habit of doing fresh water top offs (up to a certain line in my tank). When I make fresh saltwater it is usually 2.5 cups of salt per 5 gallons of water.

Well, I must have misjudged somewhere. The last time I checked my specific gravity it was somewhere between 1.025 and 1.026. When I checked my specific gravity tonight it was 1.020. Quite a drop over about six months.

So I learned a lesson, check your specific gravity. I will be bringing my specific gravity back up but I thought I would put a poll to see what everyone is currently keeping their tank at. I would like to get back up to 1.026.

Post any advice you would like to share about specific gravity and salinity here.

Thanks :)

Christopher

[MattK]

Quite a drop over about six months.

Jeez, even I check my SG every three months. :P

[Bill S]

Christopher, I used to do the same before I switched to Reef Crystals. Then I noticed that it takes about 3 cups in a 5 gallon bucket...

[NaCl_H2O]

Are you sure? How are you checking SG? Is it calibrated or verified against another source? The reason I ask is I had a similar situation once using a swing arm Hydro - I actually raised by SG to 1.028 before I asked "Am I sure the reading is accurate?".

[cbianco]

Christopher, I used to do the same before I switched to Reef Crystals. Then I noticed that it takes about 3 cups in a 5 gallon bucket...

What do you think constitutes the extra half cup per 5 gallons of water? Maybe some kind of buffer?

I currently use Oceanic. It has been good to me so far.

Christopher

[cbianco]

Are you sure? How are you checking SG? Is it calibrated or verified against another source? The reason I ask is I had a similar situation once using a swing arm Hydro - I actually raised by SG to 1.028 before I asked "Am I sure the reading is accurate?".

I'm using my good ole Deep Six. I know that it is not the most accurate piece of machinery ever made but I was under the impression that it stays accurate. I know that SG fluctuates with temperature but my temps are in the low 80, just as they have always been.

I am assuming by your post that your swing arm hydrometer kicked the bucket. Did you buy another or did you go the refractometer (sp?) route?

Christopher

http://www.petsmart.com/media/ps/images/products/detail/large/February06/lg_52138_5446d.jpg

[MKCindy]

The instructions on Red Sea Coral Pro mentions mixing if to a lower SG than required. As the water is aerated it will continue to dissolve and the SG will rise slightly. SG varies according to water temperature. Re-check before adding to tank.

The water from the jetties at Port A was 1.016, but I kept it very cool as recommended by some of the guys from the Dallas/FW area. Something about keeping the fish less active so they produce less waste, thus travel better. It worked!

[cbianco]

The instructions on Red Sea Coral Pro mentions mixing if to a lower SG than required. As the water is aerated it will continue to dissolve and the SG will rise slightly. SG varies according to water temperature. Re-check before adding to tank.

The low SG was from the current water in my tank. I am pretty sure that all the salt was disolved :P and my temp is higher than many other but stable none the less.

The low SG was from neglect. I neglected to take the SG of my tank water for many months because I thought I knew it all. I won't do that again!

Christopher

[Bill S]

I'm old fashioned. I ONLY use the large floating hydrometers - I've used them for 35 years. They might be fragile, but they NEVER need to be calibrated. And, unlike the swing arms, they never get old.

[cbianco]

I'm old fashioned. I ONLY use the large floating hydrometers - I've used them for 35 years.

Your dating yourself here... :lol


They might be fragile, but they NEVER need to be calibrated. And, unlike the swing arms, they never get old.

I may have to look into one of those. Floating hydrometers are pretty inexpensive from what I've seen.

I don't really like the swing arm. Too many factors to consider, i.e. temperature, bubbles on the arm, the arm sticking, etc... May be time for a change.

Christopher

[sawarf]

I'm old fashioned. I ONLY use the large floating hydrometers - I've used them for 35 years. They might be fragile, but they NEVER need to be calibrated. And, unlike the swing arms, they never get old.



I have two different brands of swing arms to check against each other but didn't know they could "get old." Do they actually loose calibration? how long are we talking?

[MKCindy]

Sorry, Christopher, we kinda cross posted at the same time. I was responding to Bill above. I recently changed to Coral Pro and it responds to RO water differently than my previous salt. Seems to be a finer consistence.

[caferacermike]

I use about an extra cup of Seachem when mixing up 15 gallons. It usually hits about 1.020 at the suggested rate. I think they keep it low so it is easier to fine tune with more salt. Not to mention all salt mixes recommend using weight more than a "per cup" method. The directions on IO and Seachem both say that the half cup p/g is for smaller batches and then it jumps up to a 5lb per something method. My understanding is that corals and inverts react better around 1.026 and that fish only setups run better around 1.020. There seem to be hundreds of theories why that is. the 2 that stick out the most is that you have extra trace elements for corals at the higher salinity and that parasites that attack fish have a harder time living in the lower salinity levels.

[jroescher]

I use one of these....
Digi-Lab TSS Meter
http://www.jbjnanocube.com/contents/media/JBJ_DIGILAB_tss.jpg
a little pricey but really quick and convenient.

Fair warning, one drop of salt water in the area of the battery compartment and it's history!

[NaCl_H2O]

I'm using my good ole Deep Six. I know that it is not the most accurate piece of machinery ever made but I was under the impression that it stays accurate. I know that SG fluctuates with temperature but my temps are in the low 80, just as they have always been.

I am assuming by your post that your swing arm hydrometer kicked the bucket. Did you buy another or did you go the refractometer (sp?) route?

I was using the same one you have, pulled an old one out of the cabinet and it was .002 different :unsure Took both hydros to a LFS and mine and two of theirs registered +/- .001 of each other :unsure :unsure

I bought a refractometer and a floating hydro. I cal my refractometer often and check it against the flaoting hydro

[cbianco]

Sorry, Christopher, we kinda cross posted at the same time. I was responding to Bill above.

No problem.


I was using the same one you have, pulled an old one out of the cabinet and it was .002 different Took both hydros to a LFS and mine and two of theirs registered +/- .001 of each other

I bought a refractometer and a floating hydro. I cal my refractometer often and check it against the flaoting hydro

.002 is a pretty decent variance. It is interesting to see that you calibrate the refractometer against the floating hydrometer. Is it correct to assume that this is a common practice?

Why does the swing arm hydrometer loose it's accuracy?

Why doesn't the floating hydrometer loose it's accuracy?

Is it just a plastic vs glass thing or is there more too it?

Christopher :)

[tony]

my refractometer is probly the best money ive spent in this hobby

i check its calibration often but ive yet to have to turn the screw so to speak

christopher, if you keep the swingarm clean i doubt it would lose much accuracy if any. i think their biggest problem is possible salt buildup (and bubbles) on the swingarm

i too used floating hydrometers for years and love them also but it is tricky to get the water still while taking a reading and they have become harder to find in recent years

[erikharrison]

If you want to have yours tested, take it to AD. They will test it against their refractometer.

[Bill S]

Swing arms DO fail with age. And floating ones DO break. And refractometers must be properly calibrated.

[cbianco]

my refractometer is probly the best money ive spent in this hobby...

I've heard this before.


Swing arms DO fail with age. And floating ones DO break. And refractometers must be properly calibrated.

I think that I will go by taste from now on... "Taste a bit to salty, add some fresh water..." :)

I think that I will look into buying a floating hydro for now to cross reference my swing arm hydro. Eventually, I will upgrade to a refractometer.

Christopher

[MattK]

Eventually, I will upgrade to a refractometer.

Sweet! Hopefully sooner than later.
Then I can just use yours. :D

[cbianco]

Sweet! Hopefully sooner than later.
Then I can just use yours. :D

You know, I was thinking the same thing, only you were supposed to be the one buying the refractometer.

Christopher

[caferacermike]

I've always wanted a refractometer but we had a pretty good argument here about 6 months back about how accurate they are for salt water reefs. I'm not sure anymore about the exact debate but it was something along the lines of them being built and calibrated to measure a different type of salt... Still a great place to compare to every time you check your water since it will stay accurate and have a way to calibrate it back to some reference point, unlike swing hydros.

[jroescher]

So which is more important? An exact salinity measurement or consistant salinity levels within a range.

[cbianco]

So which is more important? An exact salinity measurement or consistant salinity levels within a range.

From what I understand, natural reefs vary in salinity. I couldn't tell you to what degree though. I am sure that the fluctuation is not much, i.e. <1 ppm if that much.

I would imagine (by any means) you would want to keep your aquarium as steady as possible. If salinity changes are to be made then it would be neccesary to make them over several days. When dealing with such a small body of water (your aquarium) small changes may have large consenquences.

Christopher :)

[NaCl_H2O]

.002 is a pretty decent variance. It is interesting to see that you calibrate the refractometer against the floating hydrometer. Is it correct to assume that this is a common practice?

Why does the swing arm hydrometer loose it's accuracy?

Why doesn't the floating hydrometer loose it's accuracy?

Is it just a plastic vs glass thing or is there more too it?
Sorry, I meant +/- .002, two of the swing arm hydro's were .004 apart :o

I cal my refractometer with RO or distilled water, then check against the floating hydro to make **** sure. The floating hydro is 100% sealed & based entirely on bouyancy, no cal required as long as water temp is within the temp range for the bulb - basically a known calibration standard!

[cbianco]

The floating hydro is 100% sealed & based entirely on bouyancy, no cal required as long as water temp is within the temp range for the bulb - basically a known calibration standard!

It's funny that you mention this, I have been reading about temperature corrections as we speak. I knew of this before but never paid it much mind.

The hydrometer I have, Deep Six, is supposedly accurate regardless of temperature. Coralife says it has "automatic temperature correction."

The biggest problem from all that I have read (specifically regarding the Deep Six) is that it has a tendency to read low, really low (off by ~.003).

Christopher

[caferacermike]

I think consistency is the key. We all can agree to having good success over a broad spectrum of numbers. I'd be more worried about my tank running the range from 1.02-1.03 because of a hydrometer that reads different with each use. I'd think that if your refractometer read 1.025 but was actually 1.023, but everything did well in the tank, that in the end the refractometer would provide the most consistent results.

Even with the issues I still want one.

[LoneStar]

I think consistency is the key. We all can agree to having good success over a broad spectrum of numbers. I'd be more worried about my tank running the range from 1.02-1.03 because of a hydrometer that reads different with each use. I'd think that if your refractometer read 1.025 but was actually 1.023, but everything did well in the tank, that in the end the refractometer would provide the most consistent results.

Even with the issues I still want one.

http://forums.ircspy.com/images/smilies/goodpost7td.gif

I totally agree with that. I'm actually looking at different refractometers online. They range from cheap (Marine Depot version) $45 to $110 for a back lit one.

[tony]

I think consistency is the key. We all can agree to having good success over a broad spectrum of numbers. I'd be more worried about my tank running the range from 1.02-1.03 because of a hydrometer that reads different with each use. I'd think that if your refractometer read 1.025 but was actually 1.023, but everything did well in the tank, that in the end the refractometer would provide the most consistent results.

Even with the issues I still want one.

http://forums.ircspy.com/images/smilies/goodpost7td.gif

I totally agree with that. I'm actually looking at different refractometers online. They range from cheap (Marine Depot version) $45 to $110 for a back lit one.

i have a $45 marine depot one and a more expensive milwaukee unit ($100ish) and they are the EXACT same quality. they are different colors though.

as for backlight, totally useless IMO. i get good light at any bulb or even through my windows with the solar screens on (and they make it very dark in my house). if you need to test your salinity in the dark, well id say you have other problems that a refractometer doesnt test for :P

[LoneStar]

i have a $45 marine depot one and a more expensive milwaukee unit ($100ish) and they are the EXACT same quality.



Thanks Tony. Pretty much thought that would be the truth. The Marine Depot one is probably made by some other company (Milwaukee or someone else) and they got a contract with Marine Depot. They sell their 'name brand' units for a cheaper price with a 'no name' tag, to move more product.

[cbianco]

So, I recieved a refractometer today and let me tell you, swing arm hydrometers suck!

I made sure the refractometer was calibrated, distilled water read 0ppm.

I measured my tank water with the swing arm hydrometer and it read 1.026 or 36ppm.

I measured my tank water with the refractometer and it read 1.032 (I believe) or 42ppm.

The swing arm hydrometer was off by 6ppm. I am now in the process of lowering my salinity down to 35ppm.

What a crazy device! I will never trust a swing arm again for accuracy.

Christopher

[Bill S]

WOW! Did you by chance check with a floating hydrometer???

[cbianco]

WOW! Did you by chance check with a floating hydrometer???

No, I didn't have access to a floating hydrometer. I should have got one just for giggles and see what it said.

I'll tell you what, measuring saltiness is for the birds when it comes to using plastic swinging needles, lol.

I am cetainly glad that I checked with the refractometer, my corals probably hate me.

Christopher

[Bill S]

Well, your corals probably aren't as ticked as your fish... High salinity is tough on them.

[cbianco]

Well, your corals probably aren't as ticked as your fish... High salinity is tough on them.

I don't have any fish :P I don't believe in them :) coral only (it's easier)

Christopher

[hobogato]

also, the refractometer may not be reading correctly either. i recall matt posting a while back that they need to be calibrated with calibration fluid and not distilled water. something about them constructed to work with NaCl solution not our synthetic salt water and it causing read errors. you may search for refractometer calibration and see if you can find that old thread.

[cbianco]

also, the refractometer may not be reading correctly either. i recall matt posting a while back that they need to be calibrated with calibration fluid and not distilled water. something about them constructed to work with NaCl solution not our synthetic salt water and it causing read errors. you may search for refractometer calibration and see if you can find that old thread.

Ace, my heart can't take anymore. I will search for the thread tommorrow. BTW, I kid you not, the directions for the refractometer state that I should use distilled water for calibration. I may have to scan in the directions so that you can check them out. :)

On a side note, how is that giant tank (that we moved to your school) doing? Is it up and running yet?

Christopher

[tony]

christopher, ive checked that refractometer against almost every LFSs water in town and if it is off, they all are hehe

here is the calibration fluid

http://www.marinedepot.com/ps_ViewItem~SearchStr~pinpoint%20fluid~action~view ~idProduct~AM1437~idCategory~FITECL~category~Ameri can_Marine_Pinpoint_Salinity_Calibration_Fluid_Sal twater_Aquarium_Supplies_Testing_Equipment_Calibra tion_Solution~vendor~.html

[cbianco]

christopher, ive checked that refractometer against almost every LFSs water in town and if it is off, they all are hehe

here is the calibration fluid

http://www.marinedepot.com/ps_ViewItem~SearchStr~pinpoint%20fluid~action~view ~idProduct~AM1437~idCategory~FITECL~category~Ameri can_Marine_Pinpoint_Salinity_Calibration_Fluid_Sal twater_Aquarium_Supplies_Testing_Equipment_Calibra tion_Solution~vendor~.html

Thanks for the link Tony!

I would like to just say thanks once again for donating the refractometer to me. You have helped me greatly and I look forward to meeting you in person at one of the MAAST meeting.

On a side note, I couldn't believe how easy the refractometer is to use. Even easier than the swing arm in the sense that you don't have to dip any contraptions into your tank nor keep the contraption level.

Thanks again Tony!

Christopher :D

[matt]

Refractometers sold for the aquarium hobby are meant to measure the refraction of NaCl, not seawater. Apparently there is a difference. Plus, they're pretty inconsistent in terms of quality control. There are all sorts of stories about varying results with them. Randy Holmes-Farley wrote a coupe of good articles about this. You can use a specific pinpoint conductivity calibration fluid to calibrate hobby level refractometers at 35PPT, which is the range they need to be accurate in. Calibrating with R.O. water only insures that they'll read zero PPT correctly.

Maybe the easiest cheapest answer is to have a big glass floating hydrometer and an accurate thermometer, or use the pinpoint solution to calibrate the refractometer. as several people have pointed out, there's an acceptable salinity range, so being exactly at 35PPT is not so important.

[cbianco]

Well, I am back down to 35ppm. I did a bunch of small replacements (salt water for fresh water). My corals are starting to open back up. My candy canes, that turned whitish, are gaining their red color back.

I would like to thank Tony again for sending the refractometer. Without him, I would have just bought another swing arm.

BTW... If you are looking for a used (slightly defective) Deep Six, I have one for sale, $20. :P

Christopher

[tony]

glad to hear you put it to use christopher, i checked mine again yesterday with an lfs and they were both the same so if nothing else the refractometers are much more consistent

you should add more to the price of that hydrometer, yours seems to be lighter than the other ones. that should demand a premium ;)

haha

[cbianco]

glad to hear you put it to use christopher, i checked mine again yesterday with an lfs and they were both the same so if nothing else the refractometers are much more consistent...

The refractometer has gone to very good use. I already have other people who want to "borrow" it. You know who you are MattK ;) .


...you should add more to the price of that hydrometer, yours seems to be lighter than the other ones. that should demand a premium ;)

haha

It's the "special edition" made out of light weight, non-accurate plastic.

Christopher

[matt]

An update; I finally got around to getting some of the pinpoint conductivity calibration fluid. Premium aquatics sells this as "salinity probe calibration fluid" and it's a known standard for correct refraction at 35PPT. So, if you buy this stuff ($3.45) you can calibrate your refractometer so that it is very accurate at typical reef aquarium salinity. Calibrating a refractometer to read zero with R.O. water doesn't ensure that it will be accurate at 35PPT, especially measuring ASW as opposed to NaCl dissolved in water.

Anyhow, after all the reading I did about this, I finally tested my refractometer, which is one of the sybon one. It was right on the money, which really surprised me.

[cbianco]

Good to know. Thanks for the info matt! :)

Christopher