Best way to look for floaters in a vial?

[T&H]

So my previous source on another site sold 50ml vials. Which is nice, except that the constant use breaks the stopper down, especially when using big needles.

What’s the best way to look for floaters? It looks like I might have some small ones, but could be air bubbles too. Read somewhere to go into a dark room and use a flashlight? Curious the best way.