Oh wow! Very good to know. They have many varieties I think, is it anything else in particular other than just MG Organic? I assume you still have to really wash w/e plant you used to grow in it thoroughly prior to putting it in an established tank huh?
I rinse off the dirt just so it's off, but I used Miracle grow organic in a fish tank before capped with playsand with no ill effects to livestock. I've planted hc in my shrimp tank that still had some tiny clumps of MG on the roots and had no ill effects on livestock. I'm pretty sure treetom uses mg organic as a base in his shrimp tanks if I'm not mistaken.