Anyone have horror stories about using Kalk

[Michael]

I've heard people losing complete reef setups when using Kalk. The water just crusts up.

I was talking to my local fish store, and he said he never uses the stuff, it can be deadly. Now I know some people can be biased about one product over another...but has anyone ever had any bad experiences with Kalk that would support this? I just started using it and he made me kinda nervous.

Thanks.

Michael