# Penicillin for Fish (Fish Penicillin)

> Penicillin is the original beta-lactam antibiotic. It kills susceptible bacteria by preventing them from building cell walls. Mostly gram-positive bacteria; limited activity against gram-negative species.

Source: https://petremedyusa.com/medications/penicillin-for-fish/ · PetRemedyUSA

## Commonly used for

- Gram-positive bacterial infections
- Wounds and skin infections
- Fin rot with a gram-positive component

## Things to know

- People with penicillin allergies should wear gloves.
- Because many serious aquarium infections are gram-negative, penicillin is often paired with or replaced by another class.
- Not effective against parasites or fungi.

## Products

- [Fish Penicillin 500mg 100-Tablets](https://petremedyusa.com/products/fish-penicillin-500mg-100-tablets/): from $79.99
- [Fish Penicillin 250mg Tablets](https://petremedyusa.com/products/fish-penicillin-250mg-tablets/): from $39.20
- [Fish Penicillin 500mg 60-Tablets](https://petremedyusa.com/products/fish-penicillin-500mg-60-tablets/): from $63.99

## Frequently asked questions

### Is penicillin good for all bacterial infections in fish?

No. It works best on gram-positive bacteria. If the infection is gram-negative, other classes such as fluoroquinolones or tetracyclines are more commonly used.