{"product_id":"fish-pen","title":"Fish Penicillin 500mg (Fish Pen) Fix Pen Antibacterial","description":"\u003cstyle\u003e\n  .fph-product-copy {\n    --fph-text: #1f2937;\n    --fph-heading: #111827;\n    --fph-border: #d9dde6;\n    --fph-surface: #f8fafc;\n    --fph-surface-alt: #f3f5f8;\n    --fph-accent: #143583;\n    --fph-danger: #c62828;\n    --fph-warning: #f59e0b;\n    --fph-radius: 18px;\n    color: var(--fph-text);\n    font-size: clamp(15px, 1.05vw, 17px);\n    line-height: 1.75;\n    overflow-wrap: break-word;\n  }\n\n  .fph-product-copy,\n  .fph-product-copy * {\n    box-sizing: border-box;\n  }\n\n  .fph-product-copy .fph-section \u003e * + *,\n  .fph-product-copy .fph-acc-body \u003e * + *,\n  .fph-product-copy .fph-more-body \u003e * + * {\n    margin-top: clamp(14px, 2vw, 20px);\n  }\n\n  .fph-product-copy h2 {\n    margin: 0;\n    color: var(--fph-heading);\n    font-size: clamp(23px, 2.6vw, 33px);\n    line-height: 1.24;\n    letter-spacing: -0.02em;\n  }\n\n  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clamp(16px, 2.4vw, 22px);\n  }\n\n  \/* --- Inline Warning --- *\/\n  .fph-product-copy .fph-inline-warning {\n    color: var(--fph-danger);\n    font-weight: 700;\n  }\n\n  \/* --- Section scroll offset (kept: section ids stay linkable) --- *\/\n  .fph-product-copy [id] {\n    scroll-margin-top: 80px;\n  }\n\n  \/* --- Figure \/ infographic --- *\/\n  .fph-product-copy figure.fph-figure {\n    margin: clamp(16px, 2.4vw, 22px) 0 0;\n    padding: clamp(14px, 2vw, 18px);\n    border: 1px solid var(--fph-border);\n    border-radius: var(--fph-radius);\n    background: var(--fph-surface);\n  }\n\n  .fph-product-copy figure.fph-figure svg {\n    display: block;\n    width: 100%;\n    height: auto;\n  }\n\n  .fph-product-copy figure.fph-figure figcaption {\n    margin-top: 10px;\n    font-size: 14px;\n    color: #475569;\n    text-align: center;\n  }\n\n  \/* --- Responsive --- *\/\n  @media (max-width: 989px) {\n    .fph-product-copy .fph-card-list,\n    .fph-product-copy .fph-info-grid {\n      grid-template-columns: 1fr;\n    }\n  }\n\n  @media (max-width: 767px) {\n    .fph-product-copy {\n      font-size: 15px;\n      line-height: 1.68;\n    }\n\n    .fph-product-copy h2 {\n      font-size: clamp(22px, 7vw, 28px);\n    }\n\n    .fph-product-copy .fph-step-list li {\n      padding: 64px 16px 16px;\n    }\n\n    .fph-product-copy .fph-step-list li::before {\n      top: 16px;\n      left: 16px;\n    }\n  }\n\u003c\/style\u003e\n\u003cdiv class=\"fph-product-copy\"\u003e\n\u003csection id=\"fph-intro\" class=\"fph-section\"\u003e\n\u003ch2\u003eFish Penicillin 500mg: Penicillin for Fish and Pet Birds with Fin Rot,\u003cbr\u003ePop-Eye and Skin Ulcers\u003c\/h2\u003e\n\u003cp\u003eFish Pen (Fix Pen) is a fish penicillin 500mg tablets for ornamental aquarium\u003cbr\u003efish and non-food pet birds. Each tablet contains 500 mg of Penicillin V Potassium, made by Aqua Soma Labs in the United States, and aquarists use it for fin and tail rot, infected wounds, pop-eye and columnaris-type lesions where a bacterial cause is suspected, in both freshwater and saltwater tanks. The label amount is one 500 mg tablet per 20 gallons (76 L) of water, repeated every 24 hours for 5 to 10 days.\u003c\/p\u003e\n\u003cp\u003eAquarists may know this product as Fish Pen, Fish Pen Forte, Aqua Pen or FISHBIOTIC Penicillin. Those were Thomas Labs brand names, and Fix Pen is the current replacement now that the Thomas Labs line is discontinued. Keepers usually reach for penicillin tablets for fish when they see fin rot, tail rot, infected wounds, pop-eye (bulging eyes) or columnaris-type lesions, sometimes called cotton-wool disease, where a bacterial cause is suspected.\u003c\/p\u003e\n\u003cp\u003eStart treatment early, at the first signs of a suspected bacterial problem. The signs are not the same for fish and birds, so use the lists below to know what to watch for.\u003c\/p\u003e\n\u003cp class=\"fph-alert\"\u003e\u003cstrong\u003eImportant Notice:\u003c\/strong\u003e This product is \u003cstrong\u003eintended for aquarium and ornamental fish and pet birds only\u003c\/strong\u003e. It is \u003cstrong\u003enot for animals used for food\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cdetails class=\"fph-more\"\u003e\n\u003csummary\u003e\u003cspan class=\"fph-more-open\"\u003eSee More +\u003c\/span\u003e\u003cspan class=\"fph-more-close\"\u003eSee Less −\u003c\/span\u003e\u003c\/summary\u003e\n\u003cdiv class=\"fph-more-body\"\u003e\n\u003cp\u003ePenicillin V works on the cell walls of certain bacteria and can stop certain gram-positive bacteria from multiplying. Fix Pen is the fish penicillin 500 mg tablet many hobbyists use for fish tank infections, and the same tablets are used as penicillin for birds under avian veterinary guidance. It targets gram-positive and some gram-negative bacteria in ornamental aquarium use.\u003c\/p\u003e\n\u003cdiv class=\"fph-info-grid\"\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eFish-Specific Symptoms\u003c\/h3\u003e\n\u003cul class=\"fph-symptom-list\"\u003e\n\u003cli\u003eFin and tail rot (frayed or rotting fins)\u003c\/li\u003e\n\u003cli\u003eMouth rot and infected wounds\u003c\/li\u003e\n\u003cli\u003ePop-eye (bulging eyes) or cloudy eyes\u003c\/li\u003e\n\u003cli\u003eColumnaris-type lesions (cotton-wool look)\u003c\/li\u003e\n\u003cli\u003eOpen sores, ulcers or reddening of the skin\u003c\/li\u003e\n\u003cli\u003eReduced appetite, lethargy or hiding\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eBird-Specific Symptoms (Under Veterinary Guidance)\u003c\/h3\u003e\n\u003cul class=\"fph-symptom-list\"\u003e\n\u003cli\u003eRespiratory infections with labored breathing\u003c\/li\u003e\n\u003cli\u003eSoft tissue infections where a vet suspects bacteria\u003c\/li\u003e\n\u003cli\u003eFluffed-up feathers, lethargy or inactivity\u003c\/li\u003e\n\u003cli\u003eDecreased appetite\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp\u003eFor birds, only reach for Fix Pen when an avian veterinarian has recommended penicillin for a specific problem. Catching an infection early, paired with clean water and good husbandry, gives your fish and birds the best chance to recover.\u003c\/p\u003e\n\u003cp\u003eHusbandry still does most of the work. Stable water and good feeding prevent more problems than any treatment can fix. Penicillin does nothing for viral issues, and using fish treatments like penicillin when they are not needed can reduce how well they work later.\u003c\/p\u003e\n\u003cp\u003eEach tablet contains 500 mg, and bottles come in 30 or 60 tablets. The 30-count suits a single hospital tank or occasional use; the 60-count fits multi-tank setups or aviary needs. You can buy Fix Pen online with fresh expiration dates and U.S. shipping.\u003c\/p\u003e\n\u003cp class=\"fph-tip\"\u003e\u003cstrong\u003eOrder online:\u003c\/strong\u003e in-stock orders placed before 1:30 p.m. CT, Monday through Friday, ship the same day from our U.S. warehouse by USPS or UPS.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/section\u003e\n\u003chr\u003e\n\u003cdetails id=\"fph-comparison\" class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eFish Pen Forte vs Fix Pen: What Changed?\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cp\u003eIf you used Thomas Labs Fish Pen, Fish Pen Forte, Aqua Pen or FISHBIOTIC Penicillin, here is what is the same and what is different:\u003c\/p\u003e\n\u003cdiv class=\"fph-info-grid\"\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eSame Penicillin Formula\u003c\/strong\u003e Fix Pen contains the same 500 mg Penicillin V Potassium per tablet that you used in Fish Pen and Fish Pen Forte. The formula targets the same bacteria.\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eNew Manufacturer\u003c\/strong\u003e Fix Pen is made by Aqua Soma Labs, which replaced the discontinued Thomas Labs line. Aqua Soma Labs manufactures it in the United States.\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eSame Tablet Form\u003c\/strong\u003e Fix Pen uses the same tablet format as the original Fish Pen, so it is easy to dissolve in aquarium water or crush for precise dosing in a hospital tank.\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eAvailable in 30-Count and 60-Count Bottles\u003c\/strong\u003e Pick the size that fits your setup: a 30-count bottle for a single hospital tank or occasional use, or a 60-count bottle for larger collections, multi-tank operations or aviary needs.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails id=\"fph-benefits\" class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eBenefits of Fix Pen for Fish \u0026amp; Birds\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cul class=\"fph-card-list\"\u003e\n\u003cli\u003e\n\u003ch3\u003eTargeted Gram-Positive Bacterial Coverage\u003c\/h3\u003e\n\u003cp\u003eA classic penicillin choice when a gram-positive bacterial component is suspected in ornamental fish, especially when the signs look like fin and tail rot, mouth rot, sores, pop-eye or cloudy eyes.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eMade in the USA with Fresh Dating\u003c\/h3\u003e\n\u003cp\u003eFix Pen is manufactured in the United States by Aqua Soma Labs and ships with fresh expiration dates, so you can keep a bottle on hand for your hospital tank and trust it when you need it.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eConsistent 500 mg Tablets\u003c\/h3\u003e\n\u003cp\u003eEach tablet delivers a reliable 500 mg dose of Penicillin V Potassium, so it is easy to scale from a single betta or quarantine tank to larger community aquariums.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eCommon Aquarium Use Cases\u003c\/h3\u003e\n\u003cp\u003eOften chosen when the goal is to target gram-positive and some gram-negative bacteria in ornamental fish. In aquarium care discussions, penicillin comes up for flexibacter-type issues, infected wounds and worsening fin damage when a bacterial component is suspected.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eFreshwater and Saltwater Compatible\u003c\/h3\u003e\n\u003cp\u003eMade 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.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eQuarantine-Friendly and Biofilter Aware\u003c\/h3\u003e\n\u003cp\u003ePenicillin may affect beneficial bacteria and can be risky for invertebrates like shrimp and snails. A separate treatment tank protects the main display and makes water-quality monitoring easier during treatment.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eIdeal for Hospital Tanks and Quarantine\u003c\/h3\u003e\n\u003cp\u003eTreating in a separate hospital tank keeps the main aquarium's biofilter intact and limits exposure for healthy tank mates, so you can focus the treatment where it is needed.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails id=\"fph-dosage\" class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eUsage Guidelines \u0026amp; Instructions\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cp\u003e\u003cstrong\u003eQuick usage summary for fish:\u003c\/strong\u003e Use \u003cstrong\u003e1 tablet per 20 gallons (76 L)\u003c\/strong\u003e, repeat every 24 hours, and do a partial water change between doses. Continue for \u003cstrong\u003e5 to 10 days\u003c\/strong\u003e, and stop if you see no improvement after 5 days.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDirections for Use:\u003c\/strong\u003e\u003c\/p\u003e\n\u003col class=\"fph-step-list\"\u003e\n\u003cli\u003e\n\u003ch3\u003eSet Up a Separate Treatment Area\u003c\/h3\u003e\n\u003cp\u003eWhen possible, treat fish in a hospital or quarantine tank. This limits exposure for healthy tank mates and makes it easier to watch results and water quality. Remove activated carbon and turn off UV sterilizers during treatment, since they can strip the penicillin from the water.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eDirections for Fish Aquariums\u003c\/h3\u003e\n\u003cp\u003eDissolve \u003cstrong\u003eone (1) 500 mg tablet\u003c\/strong\u003e in a small cup of aquarium water first, then add the dissolved dose for every \u003cstrong\u003e20 gallons (76 L)\u003c\/strong\u003e of water you are treating. Repeat every \u003cstrong\u003e24 hours\u003c\/strong\u003e, with a partial water change between treatments.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eDuration and When to Stop\u003c\/h3\u003e\n\u003cp\u003eContinue for \u003cstrong\u003e5 to 10 days\u003c\/strong\u003e. If you see no improvement after 5 days, stop and consider asking an aquatic professional about next steps. Finish the full recommended number of days even if the fish look better, since stopping early can let the problem come back.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eMaintain Water Quality During Treatment\u003c\/h3\u003e\n\u003cp\u003eKeep strong aeration and watch your 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.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003ePet Birds (Under Veterinary Guidance Only)\u003c\/h3\u003e\n\u003cp\u003eFor non-food pet birds, use penicillin only under avian veterinary guidance for amount, frequency and duration. Your vet can advise the correct amount for the bird's weight and decide whether to treat a single bird or the whole flock.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003ctable class=\"fph-dose-table\"\u003e\n\u003ccaption\u003eFix Pen Amounts by Aquarium Size\u003c\/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth scope=\"col\"\u003eTank volume\u003c\/th\u003e\n\u003cth scope=\"col\"\u003ePenicillin per use\u003c\/th\u003e\n\u003cth scope=\"col\"\u003e500 mg tablets\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e10 gallons (38 L)\u003c\/td\u003e\n\u003ctd\u003e250 mg\u003c\/td\u003e\n\u003ctd\u003ehalf a tablet (split)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e20 gallons (76 L)\u003c\/td\u003e\n\u003ctd\u003e500 mg\u003c\/td\u003e\n\u003ctd\u003e1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e40 gallons (151 L)\u003c\/td\u003e\n\u003ctd\u003e1000 mg\u003c\/td\u003e\n\u003ctd\u003e2\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e60 gallons (227 L)\u003c\/td\u003e\n\u003ctd\u003e1500 mg\u003c\/td\u003e\n\u003ctd\u003e3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e75 gallons (284 L)\u003c\/td\u003e\n\u003ctd\u003eabout 1875 mg\u003c\/td\u003e\n\u003ctd\u003eabout 4\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cp\u003eThese amounts follow the label guideline of one 500 mg tablet per 20 gallons (76 L), roughly 25 mg per gallon. Dose by the water volume of your treatment tank, not by the number of fish, give one dose every 24 hours for 5 to 10 days, and make a partial water change between doses. Splitting a tablet by hand is only approximate, so for tanks under 20 gallons it is better to dissolve a whole tablet in a measured cup of tank water and add the matching fraction. Continuing for the full recommended number of days matters as much as picking the right treatment. The bottle label or your aquatic veterinarian takes priority over this quick-reference chart.\u003c\/p\u003e\n\u003ch3\u003eWhat to Expect During Treatment\u003c\/h3\u003e\n\u003cdiv class=\"fph-info-grid\"\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eDays 1 to 2\u003c\/h3\u003e\n\u003cp\u003eFish may hide or eat less, and the water can look slightly cloudy. This is normal early on. Keep dosing on schedule and keep aeration strong.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eDays 3 to 5\u003c\/h3\u003e\n\u003cp\u003eLook for signs it is working: sores and red patches stop spreading, appetite starts to return, and breathing steadies. If there is no change by day 5, or the fish look worse, stop and ask an aquatic professional.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eDays 5 to 10\u003c\/h3\u003e\n\u003cp\u003eEven if the fish are improving, finish the full treatment so the infection does not return. Afterward, run a partial water change and put activated carbon back in to clear any leftover penicillin.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cfigure class=\"fph-figure\"\u003e\u003csvg viewbox=\"0 0 760 185\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" role=\"img\" aria-labelledby=\"fixpen-tl-title fixpen-tl-desc\"\u003e\n\u003ctitle id=\"fixpen-tl-title\"\u003eFix Pen treatment timeline\u003c\/title\u003e\n\u003cdesc id=\"fixpen-tl-desc\"\u003eA typical Fix Pen treatment for aquarium fish runs 5 to 10 days. Days 1 to 2: set up and start treatment. Days 3 to 5: watch for response. Day 5: reassess and stop if there is no improvement. Days 5 to 10: finish the treatment.\u003c\/desc\u003e\n\u003ctext x=\"150\" y=\"34\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"15\" font-weight=\"700\" fill=\"#111827\"\u003eDays 1 to 2\u003c\/text\u003e\n\u003ctext x=\"150\" y=\"56\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"13\" fill=\"#475569\"\u003eSet up \u0026amp; start\u003c\/text\u003e\n\u003ctext x=\"370\" y=\"34\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"15\" font-weight=\"700\" fill=\"#111827\"\u003eDays 3 to 5\u003c\/text\u003e\n\u003ctext x=\"370\" y=\"56\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"13\" fill=\"#475569\"\u003eWatch for response\u003c\/text\u003e\n\u003ctext x=\"600\" y=\"34\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"15\" font-weight=\"700\" fill=\"#111827\"\u003eDays 5 to 10\u003c\/text\u003e\n\u003ctext x=\"600\" y=\"56\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"13\" fill=\"#475569\"\u003eFinish the treatment\u003c\/text\u003e\n\u003crect x=\"40\" y=\"86\" width=\"220\" height=\"16\" rx=\"8\" fill=\"#143583\"\u003e\u003c\/rect\u003e\n\u003crect x=\"262\" y=\"86\" width=\"216\" height=\"16\" rx=\"8\" fill=\"#4a6fb5\"\u003e\u003c\/rect\u003e\n\u003crect x=\"480\" y=\"86\" width=\"240\" height=\"16\" rx=\"8\" fill=\"#9fb3d9\"\u003e\u003c\/rect\u003e\n\u003ccircle cx=\"40\" cy=\"94\" r=\"10\" fill=\"#143583\" stroke=\"#ffffff\" stroke-width=\"3\"\u003e\u003c\/circle\u003e\n\u003ccircle cx=\"480\" cy=\"94\" r=\"10\" fill=\"#f59e0b\" stroke=\"#ffffff\" stroke-width=\"3\"\u003e\u003c\/circle\u003e\n\u003ccircle cx=\"720\" cy=\"94\" r=\"10\" fill=\"#9fb3d9\" stroke=\"#ffffff\" stroke-width=\"3\"\u003e\u003c\/circle\u003e\n\u003ctext x=\"40\" y=\"132\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"14\" font-weight=\"700\" fill=\"#111827\"\u003eDay 1\u003c\/text\u003e\n\u003ctext x=\"480\" y=\"132\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"14\" font-weight=\"700\" fill=\"#111827\"\u003eDay 5\u003c\/text\u003e\n\u003ctext x=\"720\" y=\"132\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"14\" font-weight=\"700\" fill=\"#111827\"\u003eDay 10\u003c\/text\u003e\n\u003ctext x=\"480\" y=\"154\" text-anchor=\"middle\" font-family=\"inherit\" font-size=\"12\" fill=\"#c62828\"\u003ereassess; stop if no improvement\u003c\/text\u003e\n\u003c\/svg\u003e\n\u003cfigcaption\u003eFix Pen treatment timeline: a typical 5 to 10 day treatment for aquarium fish, with a reassessment point at day 5.\u003c\/figcaption\u003e\n\u003c\/figure\u003e\n\u003cdiv class=\"fph-info-card\"\u003e\n\u003ch3\u003eWhat You Need for Treatment\u003c\/h3\u003e\n\u003cp\u003eA little setup before the first dose saves trouble later.\u003c\/p\u003e\n\u003cul class=\"fph-symptom-list\"\u003e\n\u003cli\u003eA separate hospital or quarantine tank, so you are not treating the whole display.\u003c\/li\u003e\n\u003cli\u003eA heater and an air stone or sponge filter for steady temperature and strong aeration.\u003c\/li\u003e\n\u003cli\u003eAn ammonia and nitrite test kit to keep tabs on water quality.\u003c\/li\u003e\n\u003cli\u003eA dechlorinator for the water changes between doses.\u003c\/li\u003e\n\u003cli\u003eA small net and a clean cup for gentle transfer and measuring the dose.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003cp class=\"fph-tip\"\u003e\u003cstrong\u003ePro Tip:\u003c\/strong\u003e Dose by the actual treated water volume, not the tank's advertised size, since gravel, decorations and equipment reduce usable volume. Daily observation and stable water quality matter as much as the dose.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails id=\"fph-mechanism\" class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eHow Fix Pen Works\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cp\u003eEach Fix Pen tablet contains 500 mg of Penicillin V Potassium, a penicillin that acts on the cell walls of certain bacteria. It helps control certain gram-positive bacteria, and some gram-negative bacteria, when used as directed in ornamental fish care.\u003c\/p\u003e\n\u003cp\u003eThe rest of each tablet is made up of standard ingredients that hold it together on the shelf and let it break apart and dissolve when you add it to aquarium water or a treatment setup.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails id=\"fph-safety\" class=\"fph-acc fph-acc--warn\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eSafety and Tank Notes\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cp\u003eWhen used as directed, Fix Pen usually causes no problems in ornamental fish. As with any treatment, unnecessary use, incorrect amounts or combining products can stress fish and reduce how well it works next time.\u003c\/p\u003e\n\u003cul class=\"fph-card-list\"\u003e\n\u003cli\u003e\n\u003ch3\u003eFish\u003c\/h3\u003e\n\u003cp\u003eSome fish may show short-term stress, reduced appetite or hiding during treatment. If you notice severe distress such as rapid gill movement, loss of balance, gasping at the surface or fish lying on the bottom, stop treatment, improve aeration, do a partial water change and seek aquatic veterinary or professional guidance.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eBirds\u003c\/h3\u003e\n\u003cp\u003eFor non-food pet birds, use penicillin only under avian veterinary guidance. If your bird becomes unusually lethargic, stops eating or seems unwell, stop use and contact your avian veterinarian.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eInvertebrates\u003c\/h3\u003e\n\u003cp\u003eDo not use Fix Pen in display tanks that hold shrimp, snails or other invertebrates, since penicillin may harm them or disrupt the tank. Whenever possible, move affected fish to a separate hospital tank.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eSafe use in your system\u003c\/h3\u003e\n\u003cp\u003eTreat fish in a hospital or quarantine tank whenever you can, remove activated carbon and turn off UV sterilizers during treatment, and watch ammonia, nitrite and temperature closely. Do not mix Fix Pen with other treatments unless a veterinarian advises it.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003ch3\u003eImportant safety note\u003c\/h3\u003e\n\u003cp\u003eFix Pen is intended for \u003cstrong\u003eornamental aquarium fish and non-food pet birds only\u003c\/strong\u003e. \u003cspan class=\"fph-inline-warning\"\u003eIt is not for animals raised for food.\u003c\/span\u003e Store tablets in a cool, dry place away from direct sunlight, and keep them out of reach of children and pets. Always follow the directions on the label.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails id=\"fph-shipping\" class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eShipping \u0026amp; Returns\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cdiv class=\"fph-info-grid\"\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eShipping Policy:\u003c\/strong\u003e Orders ship from our U.S. warehouse within 1 business day via USPS or UPS, with same-day dispatch on in-stock orders placed before 1:30 p.m. CT (Monday through Friday). For full shipping details, please see our \u003ca href=\"https:\/\/finepethealth.com\/policies\/shipping-policy\"\u003eshipping policy\u003c\/a\u003e.\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eRefund Policy:\u003c\/strong\u003e If there is 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 \u003ca href=\"https:\/\/finepethealth.com\/policies\/refund-policy\"\u003erefund policy\u003c\/a\u003e carefully.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-acc\"\u003e\n\u003csummary\u003e\n\u003ch2\u003eMore Fish \u0026amp; Bird Treatments\u003c\/h2\u003e\n\u003c\/summary\u003e\n\u003cdiv class=\"fph-acc-body\"\u003e\n\u003cdiv class=\"fph-info-grid\"\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Mox (Amoxicillin) 250\/500mg\u003c\/strong\u003e A treatment for fin rot, dropsy, ulcers and other bacterial infections. Available in 30-count and 100-count capsules. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-mox\"\u003eShop Fix Mox\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Zole (Metronidazole) 250\/500mg\u003c\/strong\u003e Targets anaerobic bacteria and protozoa, including Hexamita and hole-in-the-head, in ornamental fish. Available in 60-count bottles. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-zole\"\u003eShop Fix Zole\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Doxy (Doxycycline) 100mg\u003c\/strong\u003e A treatment for columnaris, respiratory infections and Mycoplasma in fish and birds. Available in 30-count and 60-count tablets. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-doxy\"\u003eShop Fix Doxy\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Zithro (Azithromycin) 250mg\u003c\/strong\u003e A treatment for fin rot, columnaris, gill disease and avian respiratory concerns. Available in 12-count and 30-count tablets. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-zithro\"\u003eShop Fix Zithro\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Cin (Clindamycin) 150mg\u003c\/strong\u003e A treatment commonly used for gram-positive bacterial infections, including skin and soft tissue concerns in ornamental fish. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-cin\"\u003eShop Fix Cin\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Sulfa (SMZ\/TMP) 960mg\u003c\/strong\u003e A combination treatment offering broad coverage against a range of bacterial infections in ornamental fish. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-sulfa\"\u003eShop Fix Sulfa\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Flex (Cephalexin) 250\/500mg\u003c\/strong\u003e A treatment for fin rot, ulcers and bacterial skin infections in fish and birds. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-flex\"\u003eShop Fix Flex\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eFix Flox (Ciprofloxacin) 500mg\u003c\/strong\u003e A treatment for gram-negative bacterial infections, including fin rot, ulcers, columnaris and septicemia in ornamental fish. \u003ca href=\"https:\/\/finepethealth.com\/products\/fish-flox\"\u003eShop Fix Flox\u003c\/a\u003e\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eBrowse all treatments\u003c\/strong\u003e Explore our complete \u003ca href=\"https:\/\/finepethealth.com\/collections\/fish-bird-antibacterials\" rel=\"noopener\"\u003e\u003cstrong\u003eFish \u0026amp; Bird Antibacterials Collection\u003c\/strong\u003e\u003c\/a\u003e for more Fix line products and related treatments.\u003c\/p\u003e\n\u003cp class=\"fph-info-card\"\u003e\u003cstrong\u003eGuides and treatment tips\u003c\/strong\u003e Visit the \u003ca href=\"https:\/\/finepethealth.com\/blogs\/fish-and-bird-antibacterials\" rel=\"noopener\"\u003e\u003cstrong\u003eFish \u0026amp; Bird Treatments Blog\u003c\/strong\u003e\u003c\/a\u003e for practical usage guides, water-care advice and treatment tips.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003chr\u003e\n\u003csection id=\"fph-faq\" class=\"fph-section\"\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdiv class=\"fph-faq-list\"\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eWhat is Fix Pen used for?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is a fish penicillin tablet (500 mg) used to help manage suspected bacterial problems in ornamental aquarium fish, especially gram-positive infections such as fin rot, tail rot, infected wounds, pop-eye and columnaris-type lesions. For non-food pet birds, use penicillin only under avian veterinary guidance for usage and treatment decisions.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eWhat is in each Fix Pen tablet?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eEach Fix Pen tablet contains \u003cstrong\u003e500 mg Penicillin V Potassium\u003c\/strong\u003e. Penicillin V works by interfering with bacterial cell wall formation, which helps control certain gram-positive bacteria when used as directed.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eWhat is the difference between Fish Pen Forte, Aqua Pen and Fix Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFish Pen, Fish Pen Forte, Aqua Pen and FISHBIOTIC Penicillin were Thomas Labs brand names for penicillin tablets sold for aquarium fish, and that line has been discontinued. Fix Pen from Aqua Soma Labs is the current replacement, with the same 500 mg Penicillin V Potassium per tablet in 30-count and 60-count bottles. The brand name and the maker changed; the tablet and its intended fish and bird use did not.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eIs Fix Pen the same as Fin Pen?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFin Pen is a separate brand of fish penicillin sold by other suppliers, not an earlier name for this product. Fix Pen is the Aqua Soma Labs version, at 500 mg of Penicillin V Potassium per tablet in 30-count and 60-count bottles. Both are penicillin tablets for aquarium fish, but strength and count differ between brands, so dose from the label on the bottle you actually have.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eWhat is the fish penicillin dosage?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eThe label amount is one 500 mg tablet per 20 gallons (76 L) of water, roughly 25 mg per gallon, repeated every 24 hours with a partial water change between doses. Continue for 5 to 10 days and stop if there is no improvement after 5 days. For tanks under 20 gallons, such as a betta hospital container, splitting a tablet by hand is only approximate, so dissolve a whole tablet in a measured cup of tank water and add the matching share. Dose by the water volume of your treatment tank, not by the number of fish.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eIs there a fish penicillin 250 mg version?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is sold only as a 500 mg tablet. Older hobby listings and other brands have offered penicillin for fish at 250 mg, which is why both strengths turn up in search results. If your plan calls for less than 500 mg, dissolve one Fix Pen tablet in a measured cup of tank water and add the matching share rather than looking for a 250 mg tablet in this line.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eCan I use Fix Pen as penicillin for pet birds?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen contains Penicillin V Potassium, the same penicillin used in avian care, so it can serve as a penicillin for birds option. Bird amounts are different from fish amounts and depend on the species and body weight, so use bird penicillin only under the direction of an avian veterinarian who can confirm a bacterial infection and set the amount and duration. Fix Pen is intended for non-food pet birds, not poultry raised for meat or eggs.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eCan I use Fix Pen for dogs, cats or chickens?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eFix Pen is labeled for ornamental aquarium fish and non-food pet birds only. It is not formulated, tested or approved for dogs, cats, chickens or other mammals and food animals. If your dog or cat needs penicillin, a licensed veterinarian should recommend the correct product and amount for that species.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eWhere can I buy penicillin for fish? Do Walmart or Tractor Supply sell it?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eYou can order Fix Pen, the current fish penicillin, directly from Fine Pet Health in 30-count and 60-count bottles of 500 mg tablets. General retailers such as Walmart, Tractor Supply, PetSmart and Petco do not carry the Aqua Soma Labs line, so a dedicated online supplier is the reliable route. In-stock orders ship from our U.S. warehouse via USPS or UPS, with same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday.\u003c\/p\u003e\n\u003ca class=\"fph-faq-link\" href=\"https:\/\/finepethealth.com\/collections\/fish-bird-antibacterials\" rel=\"noopener\"\u003eBrowse Fish \u0026amp; Bird Treatments Collection →\u003c\/a\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails class=\"fph-faq-item\"\u003e\n\u003csummary\u003eCan Fix Pen treat fungal, viral or parasitic infections?\u003c\/summary\u003e\n\u003cdiv class=\"fph-faq-answer\"\u003e\n\u003cp\u003eNo. Fix Pen is a penicillin that targets certain bacterial infections only. It does not work against fungi, viruses or parasites such as ich, flukes or worms. For fungal, parasitic or viral problems, work with an aquatic or avian veterinarian to choose the right treatment.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003chr\u003e\n\u003c\/div\u003e","brand":"Aqua Soma Labs","offers":[{"title":"500-mg (30 Count)","offer_id":50744370790639,"sku":"641664","price":35.3,"currency_code":"USD","in_stock":true},{"title":"500-mg (60 Count)","offer_id":50744370823407,"sku":"811294","price":69.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0838\/2296\/9071\/files\/fish-pen-penicillin-500mg-30-count-fish-antibacterial..webp?v=1789229498","url":"https:\/\/myfishmox.com\/products\/fish-pen","provider":"My Fish Mox","version":"1.0","type":"link"}