Please help with hydrometer..I'm confused!

[Erin2854]

Ok so I'm wanting to convert my current 27g tank to brackish for my new figure 8 who was in freshwater at the LFS. I bought a marineland instant ocean hydrometer and tried it out. Tested the water in my freshwater tank and it's showing a reading of about 1.002? So I tested my water straight from the tap and it's showing the same. I'm confused! Thanks!

[xrayjeeper83]

Did you tap it on a hard surface to make sure there are no bubbles?

[Erin2854]

Yep

[sevenyearnight]

May be dissolved solids in the tap.

[sevenyearnight]

Try using distilled or reverse osmosis water.

[Pufferpunk]

All hydrometers/refractometers need to be calibrated against a known source.

[J-P]

yep you beat me to it.

there is a calibration solution, and if you don't have that.. use distilled water and adjust it to "1.000"

Then test again.

[DrKennethNoisewater]

i had the same problem with mine. is it a major problem to just use it that way? i guess once im up to marine conditions. for now im just increasing the salinity .002 every week so its alright for now i would think. but will that cause problems when im trying to hit more exact salinity in the near future???

[J-P]

unless you go digital there really is no such thing as exact. You just want to be as close as possible to the target.

[RTR]

Even digital there is still no such thing as exact, there is only calibrated or nothing. If you do not calibrate the measuring device, you are essentially adding no information at all. A measuring devices must be calibrated and checked routinely or they are not really measuring anything.

When you want to move up 0.002 per change, and your uncertainty is 0.002, your information level is zero - no data.

As already said calibrate against good distilled water or RODI water.

[JRC3]

Level, level, level...

Inexpensive hydrometers have to be absolutely level. Many have a hole at the top to hang them, but your does not...So test each of your waters at the exact same resting place.