Hydrometer rising in tube

[fozzybeer]

Hi there
Just wondered if anyone has come across this before:
Im brewing a Bohemian Pilsner and I've had it fermenting at 10C (50F) for about 9 days.
I pitched a 2 litre starter and it is now very active.
I decided to take a hydrometer reading and to test for diacetyl.
I use a thin plastic test tube for the hydrometer.
I took my sample and gave the hydrometer a spin. It read about 1.022. The beer in the tube was very cloudy, I'm assuming this was because the yeast is so active - I could see bubbles rising.
Anyway, after a few minutes I looked at the hydrometer again and it had risen to 1.030
I spun it again and again it read 1.022. I watched it for a while and could actually see it rising, eventually back up to 1.030.
Anybody know whats going on here? Is the activity in the sample responsibly for forcing the hydrometer up.
Which reading is the most accurate?
It tasted pretty good by the way - no obvious diacetyl

 

[Ozarks Mountain Brewery]

if bubbles are still rising leave it alone come back in 4 days

 

[Nosybear]

The bubbles in the still-fermenting beer are attaching themselves to the hydrometer, making it lighter. If it's lighter, it floats higher, giving you a higher reading.

 

[Ozarks Mountain Brewery]

just a thought those bubbles could be carbonation and if so your readings can be off any way, Ive had wort carbonate while in the fermenter before