WARNING: OPINION FOLLOWS
Antibiotics and antibacterials are useful, but they have a hazardous affect on the cycle of the tank. I will only use them in an established tank as an absolute last resort. This has only happened once.
If a fish has been injured I will remove them with a net, place a spot of malkon carefully on the injury and return them to the water.This may need to be done several times. The alternative to this, if I am shifting tanks, eg siamese fighters after breeding, is to take a bag of tank water, medicate the water, put them and float them for awhile before netting them back into the tank. I prefer to use colloidal silver for the latter method because colloidal silver is less harsh, although I believe it is just as effective.
Never put colloidal silver in your tank, as it is an antibacterial and will have a very detrimental effect on your cycle.
I used colloidal silver with great effect on our rats last week. a new rat was given to us that got sick and died shortly after arriving. two days later three of her cellmates were dead, and most of my other rats were showing signs of becoming sick (they started to bite, which is out of character) I caught them all one by one, and force fed them colloidal silver with a syringe, the rats who had taken the colloidal silver are still alive, and the two that wouldn't let me handle them died.