Its safe in a controlate enviroment, when you use  medication in your aquarium you need to control the params and use this methods:

- Water change of the 40 % of the tank liters. (one time for week)
- Put in the filter active carbon for remove the medication surplus from the water.

**BUT FIRST** try to don't use medications, look for alternative methods, for example:

- Termoteraphy
- Aloe vera
- Alimentation change (green peas)