Fix Pen (Fish Pen) Penicillin 500mg 30/60ct Fish & Bird Antibiotic

Fix Pen (Fish Pen Forte) Penicillin Tablets - 500 mg

Fix Pen 500 mg is a pharmaceutical-grade, over-the-counter (OTC) penicillin fish and bird antibiotic for ornamental aquarium fish and non-food pet birds. Manufactured by Aqua Soma Labs in the United States, Fix Pen delivers 500 mg Penicillin V Potassium (Penicillin VK) per tablet and is available in bottles of 30 or 60 tablets with fresh expiration dates.

Often called Fish Pen, Fish Pen Forte, Aqua Pen or FISHBIOTIC Penicillin in the hobby community, Fix Pen is frequently sought as a reliable online alternative to discontinued Thomas Labs Fish Pen and Fish Pen Forte products. Hobbyists commonly discuss penicillin tablets for fish in connection with issues described as fin rot, tail rot, infected wounds, secondary skin infections, pop-eye (bulging eyes), columnaris-type lesions (often presenting as cotton-wool disease) or flexibacter-type problems when a bacterial component is suspected.

Penicillin V is a beta-lactam antibiotic that works by interfering with bacterial cell wall formation, which can help stop susceptible gram-positive bacteria from multiplying. When people search for "fish pen penicillin," "penicillin for fish tank," "fish penicillin 500mg" or "bird penicillin," they are typically looking for a product like Fix Pen that targets gram-positive and some gram-negative bacterial infections in aquarium settings.

Fix Pen from Aqua Soma Labs provides 500 mg per tablet and comes in bottles of 30 or 60 tablets for flexible planning whether you maintain a single hospital tank, multiple community aquariums, or need a convenient option for pet birds under veterinary guidance. Buy Fix Pen online with fresh expiration dates and reliable U.S. shipping.

Use Fix Pen when you notice early signs that may be consistent with a bacterial problem such as reduced appetite, lethargy, reddening, sores, ulcers, frayed or worsening fin damage, pop-eye or cloudy eyes in fish. For birds, use penicillin only with veterinary direction and monitoring, especially for respiratory or soft tissue infections where your vet suspects a susceptible organism. Addressing potential bacterial issues early, together with good water quality and appropriate husbandry, helps your fish and birds maintain a stable, healthy environment.

Good husbandry still matters: stable parameters, clean water, and appropriate nutrition are the foundation of a healthy aquarium or aviary. Penicillin does not help with viral problems, and using antibiotics when they are not needed can reduce future effectiveness.

Order online and enjoy same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday. Fix Pen ships directly from our U.S. warehouse via USPS or UPS.

Important Notice: This product is intended for aquarium and ornamental fish and pet birds only. It is not for human consumption or for animals used for food. We do not sell or recommend this product for human use.

Fish Pen Forte vs Fix Pen: What Changed?

If you previously purchased Thomas Labs Fish Pen, Fish Pen Forte, Aqua Pen or FISHBIOTIC Penicillin, here is what has changed and what remains the same:

Benefits of Fix Pen for Fish & Birds

• Targeted Gram-Positive Bacterial Coverage

  A classic penicillin option commonly chosen when a gram-positive bacterial component is suspected in ornamental fish, especially when signs look consistent with issues hobbyists describe as fin and tail rot, mouth rot, sores, pop-eye or cloudy eyes.

• No Prescription Required

  Fix Pen is available over the counter for aquarium and avian use, so you can start treatment promptly without waiting for a prescription. For birds, professional veterinary guidance is still strongly recommended to determine the correct dose and duration.

• Consistent 500 mg Tablets

  Each tablet delivers a reliable 500 mg dose of Penicillin V Potassium, making it easier to scale treatment from a single betta or quarantine tank up to larger community aquariums without complicated calculations.

• Common Aquarium Use Cases

  Often chosen when the label-aligned goal is to target gram-positive and some gram-negative bacteria in ornamental fish. In aquarium care discussions, penicillin is mentioned for problems described as flexibacter-type issues, infected wounds and worsening fin damage when a bacterial component is suspected.

• Freshwater and Saltwater Compatible

  Designed for ornamental aquarium use in both freshwater and saltwater setups when used as directed. A separate hospital tank is still recommended when possible to protect the main display system.

• Quarantine-Friendly and Biofilter Aware

  Penicillin may affect beneficial bacteria and can be risky for invertebrates like shrimp and snails. A separate treatment tank helps protect the main display system and makes water-quality monitoring easier during the treatment course.

• Ideal for Hospital Tanks and Quarantine

  Using Fix Pen in a separate hospital tank helps protect the main aquarium's biofilter and reduces unnecessary exposure of healthy tank mates while you focus treatment where it is needed most.

Dosage Guidelines & Instructions

Quick dosing summary for fish: Use 1 tablet per 20 gallons (76 L), repeat every 24 hours, and do a partial water change between doses. Continue for 5 to 10 days, and discontinue if no improvement is noted after 5 days.

Directions for Use:

1. Set Up a Separate Treatment Area

   When possible, treat fish in a hospital or quarantine tank. This helps limit exposure for healthy tank mates and makes it easier to monitor results and water quality. Remove activated carbon and turn off UV sterilizers during treatment, as they can remove the medication from the water.

2. Dose for Fish Aquariums

   Dissolve one (1) 500 mg tablet in a small cup of aquarium water first, then add the dissolved dose for every 20 gallons (76 L) of water to be treated. Repeat every 24 hours, and make a partial water change between treatments.

3. Duration and When to Stop

   Continue treatment for 5 to 10 days. If no improvement is noted after 5 days, discontinue use and consider consulting an aquatic professional for next-step options. Complete the full recommended course even if fish appear better, as stopping early can allow symptoms to return.

4. Maintain Water Quality During Treatment

   Keep strong aeration and closely monitor water parameters (especially ammonia and nitrite). Because penicillin may affect beneficial bacteria and can be risky for invertebrates like shrimp and snails, a separate treatment tank and close observation are strongly recommended.

5. Pet Birds (Under Veterinary Guidance Only)

   For non-food pet birds, use penicillin only under avian veterinary guidance for dosing, frequency and duration. Your vet can advise you on the correct mg-per-kg dose and decide whether to treat a single bird or an entire flock.

Pro Tip: Dose based on the actual treated water volume (not the aquarium's advertised size), since gravel, decorations and equipment reduce usable volume. Consistent daily observation and stable water quality often make the biggest difference during suspected bacterial outbreaks.

How This Medication Works

• Active ingredient: Penicillin V Potassium (Penicillin VK) 500 mg

  Penicillin V is a beta-lactam antibiotic that works by targeting bacterial cell wall formation. It binds to penicillin-binding proteins (PBPs) involved in peptidoglycan cross-linking, which can help control susceptible gram-positive bacteria and some gram-negative bacteria when used as directed in ornamental fish care.

• Inactive ingredients

  Tablet excipients that help keep the active ingredient stable on the shelf and allow the tablet to disperse and dissolve properly when added to aquarium water or treatment setups.

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