how unaccurate are swing arm hydrometers for hyposalinity???

[scubanole]

I am treating a tang for ick. I only have a swing arm hydrometer. The readings have been just under half way between 1.008 and 1.010. Are they unaccurate enough that my QT may still be above 1.010? The reason I ask is the fish now appears to be visible ick again. I don't think it is marine velvet. I tested the water and it was ph-8.2, amm.-0. trites- 0, and trates- 40, temp. 80. I did a 30% water change. I started hypo on 2/20. hypo was down to the above readings and Ick was not visible on fish by 3/2.

 

[scubanole]

thanks, I may look at using cooper since I have not been able to find anything besides the swing arm hydrometers.

 

[scubanole]

thanks for the help.

 

[musipilot]

Just a quick anecdote...I bought 2 swing arm hydrometers....I figured if they matched I could be pretty certain they were accurate. They were off by a TON...one read 1.022 and the other 1.017. I had no idea what the salinity really was. I finally broke down and bought an ATC Refractometer, (60), and found out the salinity was actually 1.019. (verified by lfs). So...I have two accurate methods now, the refractometer and the two swing arms averaged

 

[dcsg]

Just a few days ago I ran a test. Used a refractometer and a swing arm hydrometer just to see if the hydrometer was displaying correct results. Both registered the same reading. Maybe this happens only once in a thousand but will try again later.

 

[dcsg]

I would not trust a swing arm for hypo. I agree in the normal everyday readings they would work okay.