Understanding what a medication contains can often be as or more important than understanding what it treats. I’ve compiled just a few of the most common active ingredients found in many of the most popular aquarium medications. This list is not all-inclusive but may hopefully help to unravel the why’s and how’s of some medications.
Remember, some of these active ingredients have more than one use and the medications they are in may be marketed for different uses. Antibacterial medications may be included in anti-parasitic medications and some anti-parasitic ingredients may also be useful in fungal infections but the uses I’ve listed are the most common or most effective in the aquarium trade. Always remember to properly diagnose conditions and diseases before medicating and follow the manufacturer’s instructions for any medications.
Part 1: Antibacterial ingredients in aquarium medications
These ingredients of common bacterial fish medications are used to treat different types of bacterial infections. Some are broad spectrum, general medications while others are geared towards Gram-negative or Gram-positive bacteria only. The Gram designation refers to a testing system named for the scientist who developed it, Hans Christian Gram. Known as Gram Staining, bacteria samples are treated with a purple dye under microscope, the bacteria who accept the dye, and turn purple are Gram-Positive. Bacteria that do not accept the stain are Gram-Negative, and appear pink. These two groups are the largest two types of infectious bacteria. If you try a Gram-Negative medication, and it is ineffective, then you may need to switch to a Gram Positive medication. Some antibiotics may also kill off the beneficial bacteria in the aquarium, as most nitrifying bacteria are Gram-Negative, and will affect the biological stability of the system.
Amoxicillin/ Ampicillin/ Penicillin:
The “-cillins” have been well-known for decades as popular treatments for human infections, but some aquarium medications are also made with these active ingredients. All three derivatives are used to treat bacterial infections. Amoxicillin is the most broad-spectrum of the three and treats Gram-positive and Gram-negative infections. Ampicillin treats some Gram-negative infections but is most effective on Gram-positive bacteria. Penicillin is used for Gram-positive bacteria. Aquarists who are allergic to Penicillin or any other -cillin derivatives should use extreme caution if using these medications in their aquarium.
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