I left my container outside over the winter. Now I've used it a few times and I'm wondering whether it's still effective after freezing. Any experience?

What is the brand? Presumably liquid. What works in most of the clarifiers are bacteria. Seems like bacteria can be frozen and then thawed but I am not sure. I guess the answer is in the results

I just looked up pond clarifiers and found Microbe-Lift. It says do not freeze.

That was my concern, that bacteria generally prefer to be above freezing. So yes, I think my pond clarifier is dead. Thanks for checking, Mary Stella.

You are very welcome @lovesblooms