Hydrometer problems

[MarkW19]

I'm having trouble with my Instant Ocean dip and fill hydrometer, and was hoping you guys could help.

My tank is 40 gallons, and is filled with RO water. I added my salt about a week ago, to approximately the right values. I intended to add a bit more salt to increase the SG to it's correct level. But the main problem is that every time I dip my hydrometer in the water, put it on a level surface, and tap it to dislodge any air bubbles, I get very different results - sometimes the needle goes right to the top, sometimes it goes to 0.020, sometimes to 0.023, sometimes to 0.024...and all this can even happen when doing the tests straight after each other, ie. 5 consecutive tests (rinsing thoroughly with freshwater before and after each test) often produce very different results.

Has anyone any ideas? :/

FYI:-

Eheim 2327/84 thermofilter, set at 25°C; 2 x Maxijet PH1200's.


Thanks,

Mark :?

 

[WarOrks15]

ya i had the same problem when i used my swing arm. but then i bought a refractometry. i just really took the avg of all the test i did i would run a bunch till i got ones that were vary close.

 

[dralarms]

If your not rinsing the fw out completely you will get messed up readings. I almost over salted my fish because of it.

 

[snapcrackler]

Get a refractometer and save yourself the hassle, headaches and wondering. Those swingarms are a pain in butt.

 

[dralarms]

I'm beging to agree. I can test the same water 4 times and get 3 different readings. What I do now is since you have to rinse the hydro out after each use I re rinse it in tank water (or whatever water I'm testing). I seem to get more stable and reliable results.

 

[MarkW19]

Thanks for the replies - after reading up on the web a bit over the past couple of hours, I've decided to go with the RHS-10ATC hydrometer. Quite pricey (£45), but looks the business, looks quicker/easier to use, and eliminates the margin of error and unreliability that seem to plague the cheap hydrometers.

At the end of the day, once my tank is fully stocked, with expensive fish in it, £45 suddenly doesn't seem all that expensive to help keep them alive.

Cheers guys.

 

[jackdp]

Just keep in mind that hydrometers whether floating glass or swing arm are temperature dependent. If you tested your tank water with the swing arm and then rinsed it with cold freshwater and retested I would expect the results to be slightly different even thought swing arms claim to be temperature compensating.

Hydrometers are calibrated to work at a specific temperature and when your water temperature is different from the calibrated temp you will need to correct the specific gravity result. Most good hydrometers will tell you the calibrated temperature and give you a correction chart. Its also not a bad idea to check your new hydrometer for accuracy using distilled water at the calibrated temp to be sure it reads 1.000.

Refractometers are more accurate than and most are temperature compensating. You can find them online for less than $50 US.