Hydrometer Salinity

[SSalty]

I am curious how far off was your Deep Six Hydrometer compared to a refractometer. Did it read higher than the refrac. or lower? By how much?

Thanks.

[SSalty]

Bump

[Nereaga]

I found my hydrometer to read at 1.022, or somewhere close. Never really knew because the arm would float no matter how clean I kept it.

When I switched to a refractometer, my salinity was really 1.026.

Hydrometers are junk..... IMO

[DarG]

I have an old instant ocean floating arm hydrometer, probably 15 years old if not older. I dont have a refract. but I do have a lab grade floating hydrometer that is accurate. The swing arm reads about .0005 lower than the floating hyrdometer. I trust it although I know most people dont.

[rsw686]

Hydrometers are horribly inaccurate. Mine would show the tank at 1.025 and when I bought the refractometer it was really 1.030. Talk about a waste of money in salt each water change and the stress on the fish.

[Hawaiigold]

I have both the they pretty much show the same

[drstupid]

as long as you rinse them in freshwater, make sure the arm is swinging freely, and there are no air bubbles on it, most hydrometers will give you consistent readings. they will be totally wrong, but will be consistently wrong.

you can borrow a refractometer to get a trustworthy reading, and then see what the hydrometer shows. use a sharpie to mark it. the hydrometer has the advantages of being cheap, fast, easy to use, and they don't require calibration. even if you have a more accurate measuring tool they have some value.

all the tools we have in the hobby are suspect. keeping your tank consistently at 1.030 isn't going to be stressful for most fish. the red sea is around that salinity, livestock from there will prefer it. acclimating new fish to it is going to be tough, but most fish stores keep their tanks at a very low SG so you really should be matching a QT to that and slowly bringing it up to the level of your tank anyways if you are concerned about your fishes' reactions to SG.

temperature is a good example, thermometers available to our hobby (even on controllers) are wildly inaccurate. take any half dozen you've got and toss them in the same bucket and see what they all read. you're not going to afford a lab grade thermometer to get a good absolute measurement, you're going to trust what you have to tell you that your mix water is the same temperature as your tank water, or that your halides are really heating up your tank during the day.

[Haxer]

my deep six was off by .010 compared to the refractometer i just purchaced. Better than i thought it would be ...

[SSalty]

Originally posted by rsw686
Hydrometers are horribly inaccurate. Mine would show the tank at 1.025 and when I bought the refractometer it was really 1.030. Talk about a waste of money in salt each water change and the stress on the fish.

Wow , I figured it would read high.

Thanks for the info

[DarG]

It's a crap shoot. You may get a good one or you may not. I wouldnt trust one bought now. I dont know how accurate or innacurate the old Instant Oceans were back then in general when I got mine. Dont know if they were generally innacurate and I got a good one or if they were all pretty good back then. I know that mine is accurate enough. I have always rinsed after use. Fill to level mark and check on level surface, no bubbles on arm and it is always just that little bit low. For water changes I use my floating glass hydrometer, but for quick checks, my swing arm works great. I dont know how much the certified lab grade floating glass hydrometers are these days but if the certified ones are less than the refractometers it could be a good option. They dont need to be calibrated and they are accurate.