But you can't prove definitively that it's not. So it's possible, and that's the crux of his argument. It's really weak, like the "you can't prove God doesn't exist" argument that says therefore he does, but it's not invalid.
No, you can prove it doesn't affect things, but you have to actually try.
And if you use this in the tank to "scrub" anything, it will come apart. I had a physicist tell me there's no physics involved. I asked him if he used zero force then? (yes, that's a smart joke, but definitive truth)
This thing, can, and will over time, degrade from abrasion in your tank. And as it does, it's particulate matter. What consumes particulate matter in our tanks and even covers themselves in a mucous to get particulates to stick to them? Yes, corals.
Someone else chimed in another post and said, "what's the big deal, my fish eats parts of it when it breaks apart and it's still alive?!"
I think the point is proven. There's quite a few studies now on the effects of small man-made particulates affecting marine environments.
To anyone that uses it though, +1 for keeping it real and introducing pollution to your tank