Planted Tank Guru
Join Date: Jul 2010
Location: Huntington Beach, CA, USA
I've used them and found only small problems that might be different for you. I found that I wanted to do a bit more selective ferts which can't be done with prepared items. Second was the larger problem but due to my tank specifics.
I was using them in a tank full of African cichlids as I first went into trying them with plants. I was in the early learning stages of how to deal with digging and found the mbuna were a problem as they dug into the areas where the sticks were hidden. The sticks would be stirred up and the stuff that is used to make the sticks stay together would be left laying and floating around the tank. It made more mess than I wanted but then if you don't have somebody to dig them up, it would be different.
I found nothing dangerous to prohibit their use.