Hydrometer

[htfn]

I never compare with the other but I never have any issue I think....
My fish and coral are fine for a long time. If I need new one what is your recommend? They seem to be all same price range except digital? one.

[Madreefer]

I have a Vertex. I like it. You can get good ones for less than $50. Been a while since I shopped for one.

[craigwmiller]

Originally Posted by Madreefer

I used one for years. When I finally bought a refractometer I compared the two and it was bang on. Lucky I guess.

Hit and miss, but they don't seem to drift in my experience. I had one that was bang on, and another that was off by about 3ppt (but was consistently off). I also had a refract that would drift from week to week to day to day (3-5ppt swings), and another refract that was dead on for months at a time (which I still use today )

Originally Posted by htfn

I never compare with the other but I never have any issue I think....
My fish and coral are fine for a long time. If I need new one what is your recommend? They seem to be all same price range except digital? one.

I think at the end of the day you inferred the KEY to this whole thing, consistency. Unless you are unlucky to get a meter that drifts all around, you are likely OKAY so long as what you are doing stays the same

[rayjay]

I have two that I've been using now for 20 yrs but they are Sea Test swing arms, which were the best ones when Randy Holmes Farley did the hydrometer testing.
There are things to do to help ensure accuracy though.
Always "tin" the hydrometer before using it by soaking it in water a minute or two.
Fill the hydrometer with the tank water, slowly and take the reading on the second fill.
Be sure there are no bubbles on the swing arm. Even the tiniest ones screw the reading.
Take two readings and if they differ, take another to be sure which is correct.
After testing, rinse in plain water.
Once a week, soak the hydrometer in white vinegar overnight.

[mike31154]

As mentioned in several posts now, if your livestock is fine after 6 years of using it you're probably ok. On the other hand, without comparing it to a known value or another hydrometer, you'll never really know how accurate (or not) it is. Most salt mixes usually tell you on the packaging the ratio of salt to water for a given salinity value. That might be a good way to check it out without having to go out & get a refractometer or glass floating hydrometer.

I've used all three types & the floating glass hydrometer is actually quite accurate. Mine had a thermometer built in, since the floaters are calibrated at a certain temperature, so can be off a point or two if the solution you measure is significantly higher/lower than the cal temp. Most refractometers offered these days have automatic temperature compensation.

Results of measuring the same water with a floating glass hydrometer & 2 swingarms. I also used a refractometer & its reading was the same as the floating glass hydrometer @ just above 1.024.

Glass


Coralife


IO Deep Six


As is evident, both swingarms were reading lower with the Coralife low by more than 2 points. If I had been using this to mix & measure water, the solution would end up around the 1.030 mark which is probably not good long term for livestock. While I don't use the swingarms these days, I still have them & used a permanent marker to correct the scale at 1.025 in accordance with the refractometer reading. Since they work on the principle of a weighted fulcrum, there's not much reason for them to lose whatever calibration they have. Only way is for the weight to be moved along the arm or contamination caked on the arm that would change the weight. Temperature might also be a factor. Other than that, once you've confirmed it's reading with a known value, it should be fine to use as long as you keep it clean.

[htfn]

Actually I never clean my hydrometer before and I Guess I have to do that. My hydrometer effect temperature. I've been using IO since I've started and only change the salt 3,4 times. Every time I make new saltwater my reading is 1.024 but in my tank it's always 1.025. New water is 77 degrees and tank water is between 77 and 78. I have ATO, so not evaporate always same water level. I never figure out but I never think serous. I can maybe borrow one from my friend or just buy new one to compare.