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Fish Clindamycin 150mg 100 Capsules - Antibacterial for Infected Injuries in Ornamental Fish

Fish Cin (Fix Cin) 150mg 100ct

$59.99
by Aqua Soma Labs
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Fix Cin (Fish Cin) Clindamycin 150 mg Capsules / 100 Doses

Fix Cin at a Glance
For Ornamental aquarium fish (tank use only)
Helps with Fin and tail rot, mouth rot, skin ulcers and lesions, and other suspected bacterial problems
Form Capsules, 150 mg each (dissolvable powder inside)
Count sizes 100 count
Water type Freshwater and saltwater
Made in United States by Aqua Soma Labs

Fix Cin is an antibacterial treatment from Aqua Soma Labs for ornamental aquarium fish. Each capsule contains 150 mg of clindamycin in a dissolvable powder, and aquarists use it to help manage suspected bacterial problems such as fin and tail rot, mouth rot or cotton-mouth, skin ulcers, and slow-healing lesions. This bottle holds 100 capsules, which suits larger aquariums or repeat treatment.

If you used to buy Thomas Labs Fish Cin or Aqua-Cin, Fix Cin is the current replacement and uses the same clindamycin at the same strength. Aquarists reach for it when fish show fin and tail rot, mouth rot or cotton-mouth (often miscalled "mouth fungus"), bacterial dropsy, skin ulcers or lesions, swim bladder problems, or other suspected internal bacterial issues. This bottle provides 100 capsules with fresh expiration dates, enough for larger aquariums or repeat treatment.

Use Fix Cin at the first signs of bacterial stress in fish. These are the signs aquarists most often link to bacterial stress:

Fish Symptoms to Watch For

  • Clamped or frayed fins, fin and tail rot
  • Reddened areas or red streaking
  • Open sores, skin ulcers, or lesions
  • Cottony mouth damage or mouth rot (often miscalled "mouth fungus")
  • Listlessness or lethargy
  • Persistent loss of appetite

Treating early, along with clean water and strong aeration, helps protect the rest of the tank while the affected fish recovers. If your display tank contains shrimp or snails, treat the fish in a separate hospital tank to reduce risk.

Order online and get same-day dispatch on orders placed before 1:30 p.m. CT, Monday through Friday. Ships directly from our U.S. warehouse.

Important Notice: This product is intended for ornamental aquarium fish only. It is not for animals used for food.

Fish Cin vs Fix Cin: What Changed?

If you previously purchased Thomas Labs Fish Cin or Aqua-Cin, here is what has changed and what remains the same:

Same Clindamycin Formula Fix Cin contains the same Clindamycin Hydrochloride 150 mg per capsule that Fish Cin (Thomas Labs) used. The strength and capsule format have not changed.

New Maker Fix Cin is produced by Aqua Soma Labs, a maker focused on fish and bird treatments. It replaces the discontinued Thomas Labs Fish Cin and Aqua-Cin product lines.

Same Capsule Form The capsule is the same dissolvable powder form that Fish Cin keepers know, so your routine stays the same.

100-Count Bottle Fix Cin comes in a 100-count bottle, a generous supply for larger aquariums, repeat treatment, or multi-tank keepers.

Benefits of Fix Cin for Fish

  • Support for Common Bacterial Aquarium Problems

    Fix Cin is often chosen when bacterial problems show up as fin damage, mouth irritation, ulcers, or slow-healing wounds in ornamental fish.

  • Works in Freshwater and Saltwater Tanks

    Aquarists use Fix Cin in both freshwater and saltwater hospital tanks, so it fits a range of ornamental aquarium setups.

  • Helpful for External Lesions and Wound-Type Issues

    Aquarists often reach for this clindamycin when they see redness, open sores, frayed fins, or recurring skin lesions that may be linked to bacterial stress.

  • Support for Internal Bacterial Concerns

    It can be used in a treatment setup when fish show ongoing appetite loss, low activity, or digestive-type signs that can sometimes accompany internal bacterial infections, including deep tissue infections or swim bladder infections.

  • Consistent 150 mg Clindamycin Capsules

    Each capsule provides a fixed 150 mg of clindamycin, which makes it easier to plan treatment for both freshwater and saltwater aquariums.

  • 100 Capsules for Repeat Treatment and Larger Tanks

    The 100-capsule bottle is practical for community tanks, repeat treatment, and keepers who maintain a dedicated quarantine system.

  • Hospital Tank Friendly to Limit Main-Tank Disruption

    Treating in a separate hospital tank keeps the treatment where it is needed and lowers stress on the main aquarium. Monitor ammonia and aerate well during any treatment.

Usage Guidelines & Instructions

Directions for Use:

  1. Set Up a Separate Treatment Tank

    Move affected fish to a hospital tank when possible to make treatment easier and help protect healthy tank mates. If you use chemical filtration (like activated carbon), remove it during treatment, and turn off UV sterilizers if present. Increase aeration in the treatment tank.

  2. Dose by Aquarium Water Volume

    Add one capsule (150 mg) per 10 gallons (38 L) of aquarium water to be treated. For faster dispersal, many hobbyists pre-mix the capsule contents in a small cup of aquarium water first, then add it to the tank.

  3. Repeat Every 24 Hours

    Repeat the dose every 24 hours.

  4. Perform Partial Water Changes Between Doses

    Perform a partial water change between treatments to support water quality. Monitor fish behavior and basic water parameters during treatment.

  5. Continue for 5 to 10 Days

    Continue treatment for 5 to 10 days, depending on infection severity.

  6. Stop if There Is No Improvement by Day 5

    If no improvement is seen within 5 days, discontinue use and reassess the likely cause. Consider guidance from an aquatic veterinarian or fish health professional, especially if symptoms worsen.

  7. Clear Harmless Yellow Tint After Treatment

    To remove harmless yellow discoloration, change 20% of the water and run a charcoal (activated carbon) filter until the water clears.

Fix Cin Amounts by Aquarium Size
Tank volume Clindamycin per use 150 mg capsules
10 gallons (38 L) 150 mg 1
20 gallons (76 L) 300 mg 2
30 gallons (114 L) 450 mg 3
40 gallons (151 L) 600 mg 4
55 gallons (208 L) about 825 mg 5 to 6

These figures follow the label-style guideline of one 150 mg capsule per 10 gallons, roughly 15 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 round to the nearest practical capsule. The bottle label or your aquatic veterinarian takes priority over this quick-reference chart.

What to Expect During Treatment

Days 1 to 2

Fish may hide or eat less, and the water can take on a harmless yellow tint. This is normal early on. Keep dosing on schedule and keep aeration strong.

Days 3 to 5

Look for signs it is working: sores and red areas stop spreading, fins start to hold, and appetite returns. If there is no change by day 5, or the fish look worse, stop and ask an aquatic veterinarian.

Days 5 to 10

Even as the fish improve, keep treating for the full recommended number of days so the infection does not return. Afterward, change 20% of the water and run activated carbon to clear the yellow tint and any leftover product.

What You Need for Treatment

A little setup before the first dose saves trouble later.

  • A separate hospital or quarantine tank, so you are not treating the whole display.
  • A heater and an air stone or sponge filter for steady temperature and strong aeration.
  • An ammonia and nitrite test kit to track water quality.
  • A dechlorinator for the water changes between doses.
  • A small net and a clean cup for gentle transfer and mixing the dose.
  • Activated carbon to run after treatment to clear the harmless yellow tint.

Pro Tip: Antibacterial treatments can affect biological filtration in some setups, so test ammonia and nitrite and keep aeration high during treatment.

How Fix Cin Works

Fix Cin works by slowing the growth of certain bacteria, which gives the affected fish a chance to recover when treatment is paired with clean water and good care. How well it works depends on the bacteria involved and tank conditions, so it is best used when a bacterial infection is likely and alongside stable water quality.

What's inside: each capsule contains 150 mg of clindamycin as a dissolvable powder. Standard ingredients in the capsule shell hold the powder together and keep it stable in storage. The full ingredient breakdown is not printed on the retail label.

Safety and Tank Notes

When used as directed on the label, Fix Cin (clindamycin) usually causes no problems in ornamental fish. As with any treatment, incorrect amounts, combining multiple treatments, or prolonged use can increase the risk of side effects and resistance.

  • Possible Fish Reactions

    Temporary stress or hiding behavior, mild lethargy, and reduced appetite during treatment. Some tanks may show temporary, harmless water discoloration.

  • Stop Treatment and Act Quickly If You Notice

    Rapid gill movement, loss of balance, gasping at the surface, rolling over, or fish lying on the bottom. Increase aeration and consider a partial water change.

  • Support Water Quality

    Keep aeration high, test ammonia and nitrite, and perform partial water changes as needed between doses.

  • Filtration Notes

    Remove activated carbon (and other chemical media) and turn off UV sterilizers during treatment, as they may reduce effectiveness. After treatment, activated carbon can be used to help clear discoloration.

  • Invertebrates

    If your display tank contains shrimp, snails, or other invertebrates, consider treating fish in a separate hospital tank when possible.

Important Warnings & Precautions

  • For Aquarium Use Only

    Intended for ornamental aquarium fish only.

  • Not for Food Fish

    Do not use in animals raised for food.

  • Keep Out of Reach

    Store away from children and pets.

  • Storage

    Keep capsules in their original container in a cool, dry place at 59-86°F (15-30°C), away from moisture and direct sunlight. Keep the bottle tightly closed.

  • Discontinue if No Improvement

    If no improvement is seen after 5 days, stop use and reassess the likely cause. Consider guidance from an aquatic veterinarian or fish health professional if symptoms worsen.

  • Do Not Mix Treatments

    Avoid combining Fix Cin with other treatments unless advised by a professional.

Shipping & Returns

Shipping Policy: Orders ship from our U.S. warehouse within 1 business day via USPS or UPS, with same-day dispatch on orders placed before 1:30 p.m. CT (Monday through Friday). For full shipping details, please see our shipping policy.

Refund Policy: 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 refund policy carefully.

Frequently Asked Questions

What is Fix Cin used for in fish?

Fix Cin is a clindamycin treatment used by aquarists when a bacterial infection is suspected in ornamental aquarium fish. It is often chosen when bacterial problems show up as fin damage, mouth irritation, ulcers, or slow-healing wounds.

What is the difference between Fish Cin and Fix Cin?

Fish Cin was the product name used by Thomas Labs. Fix Cin is the current replacement from Aqua Soma Labs. Both contain the same clindamycin, 150 mg per capsule, in the same capsule form. The only differences are the brand name and maker.

Is Fix Cin a replacement for Aqua-Cin?

Yes. Both Fish Cin (Thomas Labs) and Aqua-Cin have been discontinued. Fix Cin from Aqua Soma Labs is the direct replacement, with the same clindamycin at the same strength.

Where can I buy clindamycin for fish online?

You can buy Fix Cin (Clindamycin 150 mg) directly from Fine Pet Health. Orders placed before 1:30 p.m. CT, Monday through Friday, ship the same day from our U.S. warehouse.

Browse Fish & Bird Treatments →
What is the active ingredient in Fix Cin (Fish Cin)?

The active ingredient in Fix Cin (Fish Cin) is clindamycin hydrochloride, 150 mg per capsule, supplied as a dissolvable powder inside the capsule. Fix Cin is made and labeled only for ornamental aquarium fish, not for animals raised for food.

How do I know if my fish might need clindamycin?

Common signs that may be linked to bacterial stress include frayed fins, red streaking, open sores, worsening mouth tissue, lethargy, or persistent appetite loss. Because different problems can look similar, confirm water quality is stable and reassess symptoms before starting any treatment.

Can Fix Cin treat fungal, parasitic, or viral problems?

No. Fix Cin targets certain bacterial infections and does not treat parasites, viruses, or true fungal infections. If you see "cottony" growth, confirm the likely cause first since mouth damage is often mislabeled as "mouth fungus."

Can I use Fix Cin in my main community tank?

Many keepers prefer treating in a separate hospital tank when possible. This helps protect healthy tank mates and makes dosing, observation, and water-quality control easier.

Is Fix Cin safe for saltwater fish or reef tanks?

Fix Cin is commonly used by both freshwater and saltwater hobbyists in a hospital tank. In reef or invertebrate systems (shrimp, snails, corals), a separate treatment tank is strongly preferred to reduce risk.

What is the recommended Fix Cin (Fish Cin) amount for fish?

A common aquarium approach is one 150 mg capsule per 10 gallons (38 L) of water, repeated every 24 hours. Follow the label directions and the usage section on this page, and support water quality with partial water changes as needed.

How long should I treat with Fix Cin?

Many hobbyists treat for 5 to 10 days depending on severity. If improvement begins, finishing the full recommended number of days can help reduce relapse as long as fish are tolerating treatment and water quality remains stable.

What if my fish shows no improvement after 5 days?

If there is no improvement by day 5, discontinue use and reassess the likely cause. Check water parameters and consider professional guidance since the problem may not be bacterial or may involve resistant organisms.

Will Fix Cin affect beneficial bacteria in my aquarium?

Any treatment like this can stress a biofilter in some setups, especially if used in the main tank. Monitor ammonia and nitrite, keep aeration strong, and consider a hospital tank to help reduce risk to established filtration.

Can I mix Fix Cin with other treatments?

Avoid combining Fix Cin with other treatments unless you have clear guidance from an aquatic veterinarian or fish health professional. Mixing products can increase stress and make it harder to identify what is helping or harming.

Can I use it as a preventive treatment?

It is generally best not to use treatments like this preventively. Unnecessary use can increase stress and may contribute to resistance, so focus on quarantine, clean water, and good husbandry unless treatment is truly needed.

Is Fix Cin safe for betta fish and small aquariums?

Fix Cin can be used in small setups when dosed correctly by water volume. Because the standard reference is per 10 gallons, measure and scale carefully to avoid overdosing, and consider a small hospital tank for easier control.

Is Fix Cin the same as fish clindamycin or Fish Aid clindamycin?

Yes. Fix Cin is the clindamycin fish treatment that hobbyists search for as fish clindamycin, fish treatments clindamycin, or Fish Aid clindamycin. The earlier Thomas Labs Fish Cin and Aqua-Cin used the same clindamycin, 150 mg per capsule. Fix Cin from Aqua Soma Labs is the current version.

Is there a Fix Cin 300 mg version?

No. Fix Cin is sold only as 150 mg clindamycin capsules. There is no single 300 mg fish clindamycin capsule in this product line. If a treatment plan calls for more than 150 mg, dose by water volume using multiple 150 mg capsules rather than looking for a 300 mg version.

How should I store and dispose of Fix Cin capsules?

Store in a cool, dry place away from direct sunlight. Keep the bottle tightly closed and out of reach of children and pets. For disposal, follow your local guidance for safe household disposal.

How soon should I see improvement with Fix Cin?

Many keepers look for early signs within the first few days, such as sores and red areas no longer spreading and fins starting to hold. If there is no change by day 5, or the fish look worse, stop and reassess with an aquatic veterinarian.

More Fish & Bird Treatments

Fix Mox (Amoxicillin) 250/500mg A treatment for fin rot, dropsy, ulcers, and other suspected bacterial infections in ornamental fish. Available in 30-count and 100-count capsules. Shop Fix Mox

Fix Zole (Metronidazole) 250/500mg A treatment for anaerobic bacterial and protozoal problems including Hexamita and hole-in-the-head in ornamental fish. Available in 60-count bottles. Shop Fix Zole

Fix Doxy (Doxycycline) 100mg A treatment for columnaris, respiratory infections, and Mycoplasma in fish and birds. Available in 30-count and 60-count tablets. Shop Fix Doxy

Fix Zithro (Azithromycin) 250mg A treatment for fin rot, columnaris, gill disease, and avian respiratory concerns in fish and birds. Available in 12-count and 30-count tablets. Shop Fix Zithro

Fix Sulfa (SMZ/TMP) 960mg A treatment for a range of suspected bacterial infections in ornamental fish. Shop Fix Sulfa

Fix Pen (Penicillin) 500mg A treatment for suspected bacterial infections in ornamental fish and non-food pet birds. Shop Fix Pen

Fix Flex (Cephalexin) 250/500mg A treatment for fin rot, ulcers, and bacterial skin infections in ornamental fish and birds. Shop Fix Flex

Fix Flox (Ciprofloxacin) 500mg A treatment for suspected bacterial infections including fin rot, ulcers, columnaris, and septicemia in ornamental fish. Shop Fix Flox

Browse all treatments Explore our complete Fish & Bird Treatments Collection for more Fix line products and related care.

Guides and treatment tips Visit the Fish & Bird Treatments Blog for practical usage guides, water-care advice, and treatment tips.

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