guys hey.. i was reading about salt in the forums and i'm not sure who it was but some one had commented that the salt should be iodine free.. i cant seem to get aquarium salt (is that iodine free?) now i just got a pack of rock salt (500gms) and the pack said it contains iodine 15 - 30 PPM (parts per million i guess).. now can i use this or not.. its for one of my silver arowanas.. he seems to bite his own tail.. or are there any other cures for this.. the water is super clean.. i change about 80 % every week and refill the amount i take out during poop clean.. let me know ppl.. cheers..