If You Use a Swingarm Hydrometer.... BURN IT NOW!

[boosted_347]

For the last 3 months I've been using an Instant Ocean hydrometer with plans on buying a refractometer down the road. I finally got my hydrometer in the mail today and calibrated it and decided to test my water.

Here's what my swing arm said:


Here's what the refractometer says my salinity actually is:


I thought the hydrometer would be REASONABLY close... but not a difference of .006.

Lesson learned. I'm glad it was caught before this tank was stocked. Has anyone else had such a big difference in results?

[gbru316]

I see several bubbles on your swing-arm hydrometer. Without those bubbles, it would probably be a little closer to the refractometer.

[cloak]

My $7.99 floating glass hydrometer seems to be spot on, so no.

[Ichabod]

I have a refractometer coming in the mail, and I'm interested to compare it to the swingarm results.

I usually have to ignore the first couple of readings (way too high, usually), and empty/fill the hydrometer a few times until I get a repeatable result, which I then take as the reading.

[ryeguyy84]

Calibrate the refractometer to the hydrometer and ...boom accurate hydrometer

[lespaul339]

Originally Posted by cloak

My $7.99 floating glass hydrometer seems to be spot on, so no.

Thats what I use as well. It works great.

[brandon429]

id burn the refract instead. one mis calibration and its wrong, the swingarm stays correct even though its a little off the refract reading. THere's no way I'll ever use a refract

[Sethjamto]

Don't care what the majority says, I use a swing arm and get accurate results and everything is nice and happy in the tank. No refract here.

[downbeach]

The only hydrometer I've ever had that was accurate, was a floating Tropic Marin unit. The only reason I stopped using it, was because it became too hard for me to read the scale. I still have my old swing arm that I use at my make up water station, it gives me an approximation when I'm adding my salt mix. But, I adjust the make up water with a refractometer before I do the WC.

[Touring]

with a refractormeter being so cheap why not get one?

[DutchLeck]

I soaked my Hydrometer overnight in the tank. Just threw it in.. once i did, it was spot on. I make sure to rinse it with RODI after every couple uses to keep it working well. So far, so good!

[Osteichthyes]

I've used a hydrometer with no problems. You just need to keep it clean and somewhat calibrate it (what I mean is make sure that its at 0 when you fill it with RO/DI water). AFter doing that all my readings seem to be accurate and everything in the tank is still looking happy

[Bpb]

I'm with the op on this one. I used a swing arm for months. Used it properly. No bubbles, cleaned meticulously every time, and when I got my refractometer, I realized I had been mixing my salt at 1.034 the whole time the swing arms were reading 1.026. I have confirmed my refractometer calibration with pinpoint solution and with 3 other local tanks as well as the lfs so it is calibrated correctly. Three swing arms I have owned have each given three different readings. Of the same water.

Since I switched to refractometer my coral health has dramatically improved. As in gone from dying to growing.

[acabgd]

Originally Posted by downbeach

The only hydrometer I've ever had that was accurate, was a floating Tropic Marin unit.

+1
I'm actually using the huge Tropic Marin hydrometer with its scale down to 0.0001 to calibrate my refractometer. Works great!

However I also have two swing arm hydrometers and they're never off more than 0.001 or 0.0015 which I find rather acceptable.

[fishgate]

What does your swing-arm read if you measure fresh RO/DI water?

[kzziboy]

I had the same Hyrdometer. It was also off by .06. The only reason I knew it was off is because my Magnesium and Calcium kept reading WAY low. Once I got the refractometer, I realized I need MORE salt. With more salt comes MORE magnesium and MORE Calcium. Now those levels look pretty good.
So, YES! It's happened to me. No more hydrometers. I'll just keep my refractometer calibrated with pinpoint solution.

[Reeferz412]

I have a swingarm. I bought it on impulse when I first started. Now it just collects dust. My refractometer gives me peace of mind. Too many stories heard about inaccurate readings and causing disasters.

[rgauvin]

My swingarm read pretty close to my hydrometer. But I was taking 3 readings and averaging them out in hopes of increasing reliability of the swing arm. Now I just use the refractometer is more consistent, more accurate, and I only need to take one reading for peace of mind.

[Palting]

I have both the swingarm and the refract. I broke the first swing arm after several months ( I stepped on it accidentally), and bought a second one. Both swing arms were fairly close to one another and to the refractometer. I find the swing arm to be more convenient and easy to use, so I use it for almost everything. Once in a while I will dust off the refractometer, calibrate it with pinpoint solution to 35 ppt, and check. Everything is spot on.

If you want a refractometer, then get one. But if you have a swing arm, don't burn it. Use it. It's fine, convenient, easy to use, IME.

[Ichabod]

Now that I have my refractometer, and have exactly one evening of experimentation to go on, I'm concluding that I prefer the sniper scope.

My method of dunking the hydrometer and taking several readings until they become repeatable does seem to get accurate results, however the refractometer is quick and easy, and takes a couple of drops to do the job.

Here's my newbie error story:
in trying to calibrate the refractometer, I followed the instructions that came on the bottle of fluid (I got the bulk reef supply door buster one), and found the screw very difficult to turn. It seemed all the way down. I did a quick search on here and found a discussion which concluded someone had a faulty unit when he couldn't adjust the screw down far enough. I tried a couple more times, and then thought I'd just try tank water for fun. As I got the little pipette (maybe?) out of the case I found a little blue screwdriver and suddenly it all made sense - I'm supposed to take off the rubber cap and use the screwdriver on the tiny screw, not try to turn the entire knurled button. . .

Anyway, then it was really easy to calibrate and really easy to use.

[amond003]

I have both and they both display the same values. Like it was stated before make sure you get out any air bubbles

[mfinn]

Originally Posted by Palting

I have both the swingarm and the refract. I broke the first swing arm after several months ( I stepped on it accidentally), and bought a second one. Both swing arms were fairly close to one another and to the refractometer. I find the swing arm to be more convenient and easy to use, so I use it for almost everything. Once in a while I will dust off the refractometer, calibrate it with pinpoint solution to 35 ppt, and check. Everything is spot on.

If you want a refractometer, then get one. But if you have a swing arm, don't burn it. Use it. It's fine, convenient, easy to use, IME.

I do pretty much the same thing.

[megadeth72]

there have been a few swingarm tests and they fail miserably

mine however matches my calibrated refractometer

[d0ughb0y]

Now you really have to wonder if the hydrometer or the refractometer is wrong. You'd be fooling yourself if you think refractometer is always right.

Hydrometer measures specific gravity based on the actual definition of specific gravity based on Archimedes principle and not through some light refraction approximation.

[megadeth72]

yeah that .1 % margin of error on a reflectometer is something to worry about LOL

I've seen hydrometers off by 10 ppt