Spirit level vials

[foresttowndiy]

Had a set of Forge Steel levels from ScrewFix last year.
Spotted yesterday the vials seem to have some kind of growth on the inside, looking very closely it appears to be specks of grit but I'm sure it is a microbe growth of some sort.
How can this happen, I don't keep them out of sunlight but what would the green solution be inside? Just coloured water or a 'spirit'?
The specks of growth hold the bubble back if the level is moved slightly which affects the accuracy. They've accepted them for return.

 

[gregers]

buy stabila levels.
the only reason ive ever in over 20 years changed my levels is when they gone out of calibration.i:e when some dumb ass(me)dropped them.

 

[muggles]

Buy crap get crap, if you use a level regularly it's worth getting decent ones that will last. I use Stanley FatMax Extreme levels, 10 year warranty on accuracy and much more solidly built than Stabila ones, they'll put up with being dropped now and then