alot of FL aquacultured is landbased aragonite type rock.It cures in the ocean and all the sponges/algae/boring organisms populate it and this coupled with it being out in the Gulf for 5yrs really helps cure it and remove some of those nasty compounds.That said,all of the FL gulf LR that i've ever bought eventually had algae issues later on.I think if your rock has cured for 50yrs in frshwater,alot of the nasty compunds should be removed.Like to see some pics of it after it populates