Fish Pen (Penicillin) 500mg – 60 Tablets

Broad-Spectrum Penicillin Treatment for Aquarium Fish

Fish Pen Tablets offer fast, reliable relief from common bacterial infections in freshwater and saltwater aquariums. Specially formulated for ornamental fish, this broad-spectrum antibiotic effectively targets gram-positive pathogens responsible for gill disease, mouth fungus, fin rot, and more.

This treatment is ideal for both beginners and advanced aquarists who want an easy-to-use solution that promotes fast recovery while limiting disease spread across the tank.

Explore more fish-safe antibiotics in our complete Fish Antibiotics Collection.

Why Choose Fish Pen?

• Targets Gram-Positive Bacteria: Kills harmful bacteria like Streptococcus and Aeromonas, eliminating infections at their source.
• Works on Multiple Conditions: Fin rot, columnaris, skin ulcers, gill inflammation, and mouth rot.
• Fast Dissolving Tablets: Simply drop into tank water or apply to food when advised by an expert.
• Speeds Up Healing: Reduces stress and visible symptoms within days of starting treatment.
• Protects the Whole Tank: Stops infection from spreading to healthy fish.

Dosage & Application

• Use one 500mg tablet per 20 gallons of aquarium water.
• Repeat daily for 5–10 days depending on severity.
• Perform a 25% water change between doses to maintain quality.
• If no improvement is noticed within 5 days, discontinue use and seek guidance.

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Storage Instructions

• Store tightly closed at 59°–86°F (15°–30°C) in a dry, cool environment.
• Keep away from children, pets, and direct light exposure.
• Do not use if product is expired — always check packaging.

Important Safety Info

• For ornamental use only. Not for fish used for food or human consumption.
• Remove all invertebrates like shrimp and snails before beginning treatment.
• Closely monitor tank levels such as ammonia, nitrite, and nitrate throughout treatment.

Read our full Shipping Policy and Refund Policy for details.

FAQs – Fish Pen 500mg 60 Tablets

• What conditions does Fish Pen treat?
  It treats gram-positive bacterial infections like fin rot, gill disease, mouth fungus, and columnaris.
• Is Fish Pen compatible with saltwater tanks?
  Yes, it can be used in both freshwater and saltwater aquariums.
• Will it harm snails or shrimp?
  Yes. Remove invertebrates before starting treatment.
• Does Fish Pen affect beneficial bacteria?
  Slightly. Monitor water quality and restore biological balance after use if necessary.
• Will Fish Pen discolor the tank?
  No, it dissolves clearly without affecting water appearance.
• Can I use it in betta or nano tanks?
  Yes, but adjust dosage based on exact water volume to avoid overdose.
• Is it safe for planted aquariums?
  Generally safe for most live aquarium plants.
• Does it expire?
  Yes. Always check the expiration date and discard outdated products.
• Where can I buy trusted fish antibiotics online?
  Order directly from DogsAntibiotics.com — fast delivery and expert support included.

Buy fish antibiotics online without a vet prescription at DogsAntibiotics.com — trusted by aquarium keepers for safe, effective, and fast-acting fish medication delivered across the USA.