Pretty much like J dub R,.... I have fed my Fronts (& probably every other fish that ever had in the approx~ 20 or so years that I've been in the Hobby),....California Black worms & although over the years I've had a few problems crop up, (very few), I can't relate them to the blackworms.
When I last participated in this subject as a VERY HEATED debate years ago on Frontosa.com, many people said that they feed their fish blackworms, but not anymore exclusively than they would any other treat & varying diet that they get. That's what I continue to do.
As far as getting them from "BIG ALS" n2t, I'm sure that if I were to tell you NO, that THAT would be talking negatively specifically about a wholesaler & I'd be in err & get another visit from one of the site Gods of Mod.
But what I can say is that there are a bunch of people who SWEAR by the quality of BIG ALS & his distributors & I've ordered from them in the past month or so on a recommendation that I got HERE! So overall I'd think you safe fromwhat I've heard.
I'll also add that the way I do it is buy my blackworms from my LFS b/c I have more of a solid, face to face, relationship with them & that contact gives me a lot of trust in them & the distributors that they choose.
Hope that helps.
LJx