Cutting root balls

Whats the consensus on cutting big root masses? I can't find any topics on the this

Why trim them? I grow in 5 gallon buckets and if they were really packed I would probably consider a bigger rez before cutting them. The only time I have ever cut roots is when they had rot.

Think: Hydro Bonsai Mums
When you trim the tops, you also have to trim the root mass. Make sure to remove any extra bits of root by rinsing. Trimming roots tends to leave a lot of little bits around. A few is fine, a lot will rot and drop pH.

Douglas