Fix Pen (Penicillin) Tablets Fish & Bird Antibiotic

Fix Pen (Fish Pen) Penicillin Tablets - Fish & Bird Antibiotic 500 mg

Fix Pen 500 mg (Penicillin) is a gram-positive focused fish and bird antibiotic for ornamental aquarium fish and non-food pet birds. In the hobby, penicillin tablets were widely known under names like Thomas Labs Fish Pen, Fish Pen Forte, Aqua Pen, or FISHBIOTIC Penicillin. Fix Pen is a modern, consistent option when you need penicillin tablets for fish and want support for suspected bacterial issues.

Each tablet contains 500 mg Penicillin V Potassium (Penicillin VK). The label describes Fix Pen 500 as used to help control gram-positive and some gram-negative bacterial infections in fish tanks and aquariums. In the hobby, it is commonly discussed for issues described as fin rot, tail rot, or “flexibacter-type” problems when a bacterial component is suspected.

Penicillin is a beta-lactam antibiotic that works by interfering with bacterial cell wall formation, which can help stop susceptible bacteria from multiplying. It does not help with viral problems, and using antibiotics when they are not needed can reduce future effectiveness. Good husbandry still matters: stable parameters, clean water, and appropriate nutrition.

Fix Pen from Aqua Soma Labs provides 500 mg per tablet and comes in bottles of 30 or 60 tablets for flexible planning in a hospital tank or quarantine setup. It can be used in freshwater and saltwater systems, and bird use should be only under avian veterinary guidance due to species-specific dosing.

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.

Use Fix Pen when you notice early signs that can be consistent with a bacterial problem such as reduced appetite, lethargy, reddening, sores, ulcers, or worsening fin damage in fish. For birds, use penicillin only with veterinary direction and monitoring, especially for respiratory or soft-tissue concerns where your vet suspects a susceptible organism.

What Are the Benefits of Fix Pen (Fish Pen) Penicillin 500 mg Tablets 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, or cloudy eyes.

• Consistent 500 mg Tablets
  Each tablet delivers a consistent 500 mg dose (often listed as Penicillin V Potassium on ingredient panels), which helps you plan treatment without complicated conversions.

• Common Aquarium Use Cases
  Often chosen when the label-aligned goal is to target gram-positive and some gram-negative bacteria. In aquarium care discussions, it is sometimes mentioned for problems described as “flexibacter-type” issues and worsening fin damage when a bacterial component is suspected.

• Flexible to Use in a Hospital Tank
  Tablets are commonly used by dissolving in treatment water in a separate hospital or quarantine tank, helping you focus treatment and observe progress while limiting unnecessary exposure of healthy tank mates.

• Freshwater and Saltwater Compatible
  Designed for ornamental aquarium use in both freshwater and saltwater setups when used as directed.

• 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.

• Helps You Stay Consistent During Treatment
  A clear tablet format supports consistent day-to-day routines and observation (behavior, appetite, and water quality trends), which can be just as important as the medication itself during a suspected bacterial outbreak.

How to Dose & Use Fix Pen (Fish Pen) Penicillin 500 mg for Fish & Birds

Quick dosing summary for fish (label): Use 1 tablet per 20 gallons (about 76 L), repeat every 24 hours, and do a partial water change between doses. Continue for 5–10 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.

2. Dose for Fish Aquariums (Label Directions)

   • Dissolve one (1) 500 mg tablet in a small cup of aquarium water first, then add the dissolved dose for every 20 gallons (about 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 5–10 days. If no improvement is noted after 5 days, discontinue use and consider consulting an aquatic professional for next-step options.

4. Maintain Water Quality During Treatment

   • Keep strong aeration and closely monitor water parameters (especially ammonia and nitrite).

   • Activated carbon and some chemical filtration media can remove medications from water. Consider taking them out during treatment and reinstalling after the course is finished.

   • 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. If you keep invertebrates, consider moving them out before dosing.

5. Pet Birds (Under Veterinary Guidance Only)

   • For non-food pet birds, use penicillin only under avian veterinary guidance for dosing, frequency, and duration.

6. Storage (Label)

   • Storage: Keep container tightly closed and store in a cool, dry place.

Pro Tip: Dose based on the actual treated water volume (not the aquarium’s advertised size). Consistent daily observation and stable water quality often make the biggest difference during suspected bacterial outbreaks.

What Makes Fix Pen (Fish Pen) Penicillin 500 mg Effective?

• Active ingredient: Penicillin V Potassium (Penicillin VK) (500 mg per tablet)
  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 bacteria when used as directed in ornamental fish care.

• Inactive ingredients:
  Tablet excipients that help keep the active ingredient stable on the shelf and help the tablet dissolve and disperse evenly in treatment water for consistent distribution.

Shipping & Returns

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Refund Policy: If there’s an issue with your order, you may be able to return or exchange items within 30 days according to our store guidelines. Before sending anything back, please review our refund policy carefully.

FAQs About Fix Pen (Fish Pen) Penicillin 500 mg for Fish & Birds

What is Fix Pen used for in fish and birds?
Fix Pen (Penicillin 500 mg) is a penicillin-based fish antibiotic used by hobbyists to help manage suspected bacterial problems in ornamental aquarium fish (often discussed as gram-positive associated issues such as fin rot or gill disease). For non-food pet birds, penicillin should be used only under avian veterinary guidance for dosing and treatment decisions.

Is Fix Pen the same as Thomas Labs Fish Pen, Fish Pen Forte, Aqua Pen, or FISHBIOTIC Penicillin?
Those are popular legacy names from the hobby. Fix Pen is a modern, clearly labeled option commonly sold in 500 mg tablet form. Always follow the label directions for your specific product.

What is the active ingredient in Fix Pen 500 mg?
Fix Pen 500 is commonly listed as Penicillin V Potassium (Penicillin VK), 500 mg per tablet. Penicillin is a beta-lactam antibiotic that works by interfering with bacterial cell wall formation, which helps control susceptible bacteria when used as directed.

How do I dose Fix Pen 500 mg for fish?
Follow the label: add one (1) 500 mg tablet per 20 gallons of water to be treated, repeat every 24 hours, and make a partial water change between doses. Continue for 5–10 days, and discontinue use if no improvement is noted after 5 days.

How long should I treat with Fix Pen?
Label directions recommend extended medication baths for at least 5 days but no more than 10 days. If there is no improvement after 5 days, discontinue treatment and reassess husbandry and next-step options.

Can Fix Pen be used in saltwater tanks?
Yes. Fix Pen is commonly used in both freshwater and saltwater aquariums. A separate hospital tank is still recommended when possible.

Can I treat in my main community tank or a reef tank?
It is usually best to treat sick fish in a separate hospital tank. Antibiotics may impact beneficial bacteria and can be risky for shrimp, snails, corals, and other invertebrates, so dosing a display tank or reef setup is generally not recommended when invertebrates are present.

Will Fix Pen affect beneficial bacteria (the biofilter)?
It can. Antibiotics may impact beneficial filter bacteria, especially if you treat in the main tank. Monitor water parameters closely (especially ammonia and nitrite), and consider using a hospital tank to protect your display system.

Is Fix Pen safe for invertebrates like shrimp and snails?
Generally no. Penicillin may harm invertebrates. When possible, remove shrimp, snails, and other invertebrates before treatment and use a separate hospital tank.

Can I use Fix Pen for betta fish?
Many hobbyists use penicillin products for bettas when dosed correctly. Dose based on the actual treated water volume and monitor closely for stress since individual fish and tank conditions vary.

Does Fix Pen discolor the water?
Fix Pen tablets are commonly described as dissolving clearly and should not dye the water. If you notice cloudiness during treatment, focus on aeration and water-quality monitoring.

Is Fix Pen safe for live aquarium plants?
It is generally considered compatible with most planted tanks, but a hospital tank is still the safest approach to reduce plant and biofilter exposure during antibiotic treatment.

How should I store Fix Pen tablets, and does Fix Pen expire?
Keep the lid tightly fastened and store in a cool, dry place away from light and moisture. Yes, Fix Pen expires. Check the expiration date on the packaging.

Can Fix Pen treat fungal, viral, or parasitic infections?
No. Penicillin is an antibiotic that targets certain bacterial infections. It is not intended for fungal, viral, or parasitic problems. If you are unsure what is affecting your fish, focus on water quality and consider consulting an aquatic professional.

How should I dispose of unused or expired tablets?
The best option is a local medicine take-back program. If a take-back option is not available, follow FDA/EPA guidance for household medication disposal and avoid flushing unless the label specifically instructs it.

More Fish & Bird Antibiotics

Need another aquarium fish or pet bird antibiotic? Explore our Fish & Bird Antibiotics Collection for more Fix line and related treatments.

Looking for dosing and water-care advice? Visit the Fish & Bird Antibiotics Blog for practical guides and treatment tips.