mixed density readings

[mvp93006]

Ive been usin an instant ocean hydrometer for years, last week i saw a red sea hydrometer and i fell in love with its smaller size
so i purchased it. The problem is that im getting different readings from both sources.Trying to find a happy medium between the two i purchased a coralife hydrometer. Too my suprise the reading from the coralife was also different. So my question is which hydrometer do i trust to use. Here are my readings

CORALIFE- 1.022
RED SEA- 1.024
INSTANT OCEAN- 1.026

I am currently using instant ocean salt mix. and my parimeters are

specific gravity- ?
alkalinity- 12
ph- 8.0
calcium- 520
magnessium- unknown orderd test kit, but it has not
arrived yet.
temp.- 80

[HighlandReefer]

I would not trust any of the hydrometers. They are notoriously inaccurate.
I would purchase a refractometer and properly calibrate it with the correct calibrating fluid not rodi water. Use the refractometer to calibrate your hydrometers. You have to be careful about bubbles on the arms of hydrometers.

[mvp93006]

<a href=showthread.php?s=&postid=15186456#post15186456 target=_blank>Originally posted</a> by HighlandReefer
I would not trust any of the hydrometers. They are notoriously inaccurate.
I would purchase a refractometer and properly calibrate it with the correct calibrating fluid not rodi water. Use the refractometer to calibrate your hydrometers. You have to be careful about bubbles on the arms of hydrometers.



Thanks for the info I think ill do that. Will any specific brand be better or are they all the same

[HighlandReefer]

Sybon seems to be a good economical brand. This a good example of the price. Make sure you get the Pinpoint-Salinity calibrating FLUID - 53.0MS also. The Pure water that comes with the kit is not good enough for salt water testing:

http://www.premiumaquatics.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=REFRACT-HD&Category_Code=Sybon-probe&Store_Code=PA

[Percula9]

Hydrometers are worthless pieces of plastic, and they should stop making and selling them. They do more harm then good. A good refractometer or conductivity meter should be used.

[bertoni]

It's possible to calibrate the hydometers with a reference solution, although I agree that hydrometers tend to be error-prone. If you'd like to mix up a simple solution for calibration, this article should help:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

[Percula9]

I agree they can be calibrated to a point. Though as time goes by they move further away from calibration. I feel its not worth the trouble to try. Its better to invest in a good refractometer and calibration solution.