I have had no problems with fluke tabs melting my plants, however if you have any catfish in your tanks be very careful because the fluke tabs will kill them especially cory cats and oto cats some of the bigger sucker mouths seem to do alright but watch them closely. I have been using one less tab than the recomended dose and have not lost any catfish or plants ie for my 55 gal I use 4 tabs instead of 5.