implies that it isn't

Yes that's correct. It's generally labor intensive or considered impossible with the current state of our oceans and pollution. Another reason to be for environmental programs, helps you stay able to use organic compounds. Granted, risk is currently low, but if we can avoid risk, we should.

Yep, bioaccumulation is neat asf. Sunflowers can be used to clear irradiation, heavy metals, etc. Really good for soil remediation. Plant, grow, burn or melt, and you're left with a way more containable problem substance. But that also means if you feed with something tainted and that plant can uptake it, it generally will.

Yeah thrive alive will totally pop ya, big grows stay away from things like that because they are detectable in state required testing. That said, risk is assumed and your body is yours, we've been growing organics like that forever with minimal issues. I'd say it's definitely a thing to keep an eye on in the future with all the pollution, and if it can be avoidable obviously cool, but otherwise I doubt it'd kill you lol.

Love Hydroguard and the entire botanicare line, haven't had a dud product from them yet.

A bigger concern for me with kelp and seaweed extracts is heavy metal/arsenic accumulation.Here is a random article I found when you Google that, lots more around. But yes, generally organics will end up with some type of root funk, as organic material helps those things breed.

H2o2 wouldn't negate, necessarily. What the plant has already used from the nutes, it's used. But would probably remove it from your water, stopping further effects. If you go that route I'd just say reapply the seaweed after the cleanse protocol you pick.

A way to avoid this in the future is root inoculations. It's a newer thing, so still lots to learn, but the idea is early on and throughout the cycle, adding in beneficial bacterias and fungal colonies that either help your plant or at the least out compete things that would harm your plant. This is a big organics move so if you're in to organic grows I'd look in to that for your next go!

Browning of roots is usually a sign of fusarium or Pythium, or a number of 'root rots', and biofilms. These are common,especially in hydro grows as they can propogate in the water. Look in to root cleansers, there are a few options. Some people will also do runs of an acid or peroxide, but my experience is with large scale fertigated grows and not hydro/aquaponics, so I couldn't suggest a solid method. Please keep in the loop if you go that route though, I'm interested.

How'd you take that picture while going fifty lol