Using Antibiotics

I'm certainly not going to recommend any antibiotics here, but I would like to offer some general observations. The first set is on modes of administering antibiotics. There are three principle options, listed from most effective to least:

  1. Injection. Based on a diagnosis of the pathogen and the fish's body mass, an appropriate selection and amount of antibiotic can be injected.
  2. Ingestion. The antibiotics can be placed into the food. Gel foods are particularly suitable, since the medicine has less opportunity to leach out into the tank water before being eaten. A dosage must be calculated based on the amount fed and the fish's mass. Both Tetra and Romet make premedicated pellets. The idea is that the antibiotic is absorbed as it passes through the digestive track.
  3. Immersion. The antibiotics are dissolved in the tank water or in a bucket for a short term dip. This is the most common and least effective method, since many antibiotics are composed of molecules that are too large to pass through the skin or gills. So they end up being topical treatments. In some cases, this may be adequate, particularly for secondary infections associated with injury or stress.

If you have a situation where you are confident that an antibiotic is appropriate and you plan to use method (3) above with the antibiotic dissolved in the tank water, here are some general suggestions:

  1. Don't mix a lot of different chemicals in the water. Stress Guard has been reported to precipitate some antibiotics out of solution, as an example. Salt should be pretty safe, but it is very difficult to anticipate the result of mixing medicines, water treatments, etc. If you don't have a good diagnosis of the disease, and are bound and determined to use an antibiotic, pick a broad spectrum antibiotic (there are many over the counter ones available in pet shops) and use it alone for the recommended period, before trying anything else.
  2. I turn off my filter immediately before adding medicines to the tank and usually leave it off for 6 to 12 hours. This may not be a good idea for everyone; you'll have to judge what is best for your setup. My goal is to try to minimize the damage to my biofilter. Many medicines decline markedly in potency in the first few hours they are in the tank water. So my filter doesn't get exposed to the full potency of the medication if I turn it off during this initial period.
  3. If you lose a fish after treating it, put it in the garbage or bury it. Don't put it down the toilet. There are enough antibiotic-resistant bacterial strains in the environment as it is, without introducing new one into waste water.