Hi,was worried about the same thing,ive added tonic salt to help with my meds in my 50 gallon tank which is very heavily planted and contains corys,but ive never had any plant probs and my corys are also fine,i was confused because i kept getting mixed reactions to this question. Everything will be fine as long as you dont use it for long periods of time and do a few water changes over a few days so the salt level dissapears after your treatment of course,hope this helps