Fix Sulfa (Fish Sulfa) 960 mg Tablets for Fish - Sulfamethoxazole & Trimethoprim (SMZ/TMP)
Fix Sulfa 960 mg (often called Fish Sulfa, Fish Sulfa Forte, FISHBIOTIC SMZ/TMP, or Aqua Sulfa in older hobby listings) is a trusted fish antibiotic for ornamental aquarium fish. This sulfamethoxazole & trimethoprim combination (SMZ/TMP) is commonly used by aquarists to help manage suspected bacterial infections in ornamental fish associated with issues like fin and tail rot, columnaris, skin sores and ulcer-like lesions, and other persistent bacterial symptoms in freshwater and saltwater aquariums.
SMZ/TMP (co-trimoxazole) is a dual-ingredient antibiotic combination that works by interfering with bacterial folate synthesis at two steps, which helps slow or stop the growth of susceptible bacteria. When used as directed for fish, sulfamethoxazole/trimethoprim is best paired with stable water parameters, strong aeration, and good husbandry to support recovery.
Fix Sulfa provides a consistent 960 mg tablet format and is available in bottles of 30 or 60 tablets, giving hobbyists flexible options for quarantine tanks, hospital tanks, and multi-tank fish rooms. It is a convenient choice when you are specifically searching for fish sulfa 960 mg tablets or sulfamethoxazole trimethoprim for fish and want a straightforward, repeatable dosing format.
Important Notice: This product is intended for aquarium and ornamental fish 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 Sulfa when you notice early signs of bacterial stress such as frayed or rotting fins, red streaking, inflamed sores, cloudy patches, lethargy, or a persistent loss of appetite that does not improve with basic water-quality corrections. Whenever possible, treat in a separate hospital or quarantine tank for better control and observation.
Addressing potential bacterial issues early with SMZ/TMP treatment, together with clean water and appropriate isolation when possible, helps support a stable, healthier aquarium environment.
What Are the Benefits of Fix Sulfa (Fish Sulfa) SMZ/TMP 960 mg Tablets for Fish?
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Dual-Action SMZ/TMP Combination
Fix Sulfa combines sulfamethoxazole and trimethoprim (SMZ/TMP), a paired approach that interferes with bacterial folate production at two steps to help manage susceptible bacterial issues when used as directed.
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Broad-Spectrum Support for Common Aquarium Problems
Aquarists commonly reach for fish sulfa tablets when dealing with symptoms associated with fin and tail rot, columnaris-type presentations, ulcer-like lesions, and other persistent bacterial signs in ornamental freshwater and saltwater fish.
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Helps With External and Internal Signs of Bacterial Stress
SMZ/TMP fish antibiotic tablets are often used in a hospital tank for visible skin sores and fin damage, and in situations where fish show lethargy or reduced appetite alongside water-quality corrections and supportive care.
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Consistent 960 mg Tablet Strength
Each tablet provides a consistent 960 mg SMZ/TMP format, making it easier to plan repeatable dosing across different tank sizes. Available in 30- or 60-tablet bottles.
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Intended for Ornamental Fish Use
Fix Sulfa is intended for aquarium and ornamental fish use when used as directed, and the tablet format offers a straightforward option for hobbyists who prefer predictable, countable dosing.
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Helpful for Quarantine and Hospital Tanks
Treating in a separate hospital or quarantine tank can help you observe fish more closely, control dosing more precisely, and reduce unnecessary exposure for healthy tank mates during treatment.
How to Dose & Use Fix Sulfa (Fish Sulfa) SMZ/TMP 960 mg Tablets for Aquarium Fish
Looking for a clear Fix Sulfa dosage for fish? The steps below follow the Fix Sulfa 960 bottle label directions for SMZ/TMP use in ornamental aquarium fish.
Dosage Quick Reference (Label):
Dissolve one (1) dose (one tablet) and add it for every 40 gallons (151 L) of water to be treated. Repeat every 24 hours with a partial water change between treatments for 5-10 days. Discontinue use if no improvement is noted after 5 days.
Before You Dose:
- Calculate actual water volume (account for substrate, decor, and fill level).
- Use a hospital/quarantine tank when possible for better control and observation.
- Remove activated carbon and other chemical media; turn off UV sterilizers during treatment.
- Increase aeration and surface agitation; keep temperature stable.
Directions for Use:
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Dissolve and Add the Dose
Fully dissolve one (1) dose (one tablet) in a small cup of aquarium water, then add the dissolved dose to the treatment tank. Dose at one (1) dissolved dose (one tablet) per 40 gallons (151 L) of water to be treated.
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Repeat Every 24 Hours (With Water Change Between Treatments)
Repeat dosing every 24 hours. Perform a partial water change between treatments throughout the course.
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Complete the Course and Watch for Progress
Continue treatment for 5-10 days. Watch appetite, swimming behavior, fin condition, and any signs of stress. Discontinue use if no improvement is noted after 5 days. If fish appear worse or show severe stress, stop treatment and seek aquatic veterinary advice.
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Post-Treatment Clean Up
After the course is complete, perform a partial water change and resume normal filtration. Replace activated carbon or chemical media if you removed it, and keep monitoring water parameters for several days to confirm stability.
Pro Tip: Hospital tank treatment helps protect the display aquarium, keeps dosing consistent, and makes it easier to keep ammonia and nitrite at 0 during recovery.
What Are the Ingredients in Fix Sulfa (Fish Sulfa) SMZ/TMP 960 mg Tablets?
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Active ingredients (each tablet):
Sulfamethoxazole 800 mg + Trimethoprim 160 mg (SMZ/TMP, also known as co-trimoxazole). This paired combination works at two steps in bacterial folate synthesis, which helps slow the growth of susceptible bacteria when used as directed.
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Inactive ingredients:
Tablet excipients that help keep the active ingredients stable and allow the tablet to disperse properly when dissolved and added to aquarium water as directed. Inactive ingredients are not specified in the active-ingredient panel.
Side Effects & Safety Tips for Fix Sulfa (Fish Sulfa) SMZ/TMP 960 mg
Individual fish can respond differently to treatment. For best results and safety, follow the label directions and monitor fish and water quality closely throughout the course.
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Possible side effects in fish: temporary reduced appetite, mild lethargy or hiding behavior, and occasional water cloudiness during treatment. If fish show severe distress such as rapid gill movement, gasping at the surface, loss of balance, or lying on the bottom, stop treatment, increase aeration, and seek aquatic veterinary advice.
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Sensitive fish: stressed, weakened, or delicate species may react more strongly. Using a hospital tank makes it easier to observe fish and control dosing and water conditions.
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Water quality and biofilter awareness: keep aeration strong and monitor ammonia and nitrite closely during treatment. If parameters rise, perform partial water changes as needed to keep the treatment tank stable.
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Invertebrates and display tanks: if your system includes shrimp, snails, corals, or other invertebrates, treat fish in a separate hospital or quarantine tank whenever possible to reduce risk to the display ecosystem.
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Do not mix medications unless instructed: avoid combining Fix Sulfa with other antibiotics or medications unless the product label explicitly allows it or an aquatic veterinarian advises it.
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Important safety warning: Fix Sulfa is intended for aquarium and ornamental fish only. It is not for human use and not for animals raised for food. Always follow the directions on the label, and discontinue treatment if no improvement is noted after 5 days (per label guidance).
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Storage: keep the container tightly closed in a cool, dry place away from direct sunlight, and keep out of reach of children and pets.
Shipping & Returns
Shipping Policy: Orders ship from our U.S. warehouse within 1 business day via USPS or UPS, with rates and delivery times calculated at checkout. For full shipping details, please click here.
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 Sulfa (Fish Sulfa) SMZ/TMP 960 mg Tablets for Aquarium Fish
What is Fix Sulfa used for?
Fix Sulfa (SMZ/TMP) is used by aquarists to help manage susceptible bacterial issues in ornamental aquarium fish when used as directed. It is commonly chosen for symptoms associated with fin and tail rot, ulcer-like lesions, and other persistent bacterial signs.
Is Fix Sulfa the same as Fish Sulfa, Fish Sulfa Forte, FISHBIOTIC SMZ/TMP, or Aqua Sulfa?
These names are often used in older hobby listings for SMZ/TMP fish antibiotic products. Fix Sulfa contains the same two active ingredients, sulfamethoxazole and trimethoprim (SMZ/TMP), in a 960 mg tablet format.
What are the active ingredients in each Fix Sulfa tablet?
Each tablet contains sulfamethoxazole 800 mg and trimethoprim 160 mg (SMZ/TMP), a paired combination also known as co-trimoxazole.
What is the Fix Sulfa dosage for fish?
Follow your bottle label directions. The Fix Sulfa 960 label instructions state: dissolve and add one (1) dose (one tablet) per 40 gallons (151 L) of water to be treated, repeat every 24 hours with a partial water change between treatments for 5-10 days, and discontinue use if no improvement is noted after 5 days.
Should I treat in the main tank or a hospital tank?
A hospital or quarantine tank is recommended whenever possible. It makes dosing easier, helps you monitor fish closely, and can reduce disruption to the display aquarium’s biofilter and tank mates.
Do I need to remove activated carbon or turn off UV during treatment?
Yes. Activated carbon and other chemical media can remove medications from water, and UV sterilizers may reduce medication availability. Remove carbon/chemical media and turn off UV during treatment, then resume normal filtration after the course is complete.
Will Fix Sulfa harm beneficial bacteria in the aquarium?
Any antibiotic treatment can affect beneficial filter bacteria, especially if used in the main tank. Monitor ammonia and nitrite closely, maintain strong aeration, and perform partial water changes as needed. Using a hospital tank helps protect the main biofilter.
Do I need water changes during Fix Sulfa treatment?
Yes. The label directions specify a partial water change between treatments during the course. Water changes also help keep ammonia and nitrite under control, especially in a hospital tank.
Can I feed my fish during treatment?
If your fish are still eating, offer small amounts and avoid overfeeding to protect water quality. If appetite drops during treatment, focus on stable water conditions and remove uneaten food promptly.
Can I use Fix Sulfa in a planted tank or with shrimp and snails?
If your system includes sensitive plants, shrimp, snails, corals, or other invertebrates, it is best to treat fish in a separate hospital or quarantine tank. This reduces risk to the display ecosystem and helps keep conditions stable during treatment.
Can Fix Sulfa treat fungal, viral, or parasitic infections?
Fix Sulfa (SMZ/TMP) is an antibiotic intended for susceptible bacterial issues. It is not designed for fungal, viral, or parasitic problems. If you suspect fungus, parasites, or mixed causes, consult an aquatic veterinarian or experienced aquarist to choose an appropriate treatment plan.
How quickly should I see improvement?
Improvement depends on the cause of symptoms, fish condition, and water quality. Monitor daily and keep water parameters stable. If no improvement is noted after 5 days, discontinue use as stated on the label and re-evaluate the diagnosis.
What if my fish are not improving?
If no improvement is noted after 5 days, discontinue use as stated on the label. Re-check water parameters, confirm the likely cause of symptoms, and seek aquatic veterinary advice or consider an alternative approach based on a more accurate diagnosis.
How should I store Fix Sulfa tablets?
Keep the container tightly closed and store in a cool, dry place away from direct sunlight. Keep out of reach of children and pets.
More Fish Antibiotics
Need another aquarium fish antibiotic? Explore our Fish Antibiotics Collection for more Fix line and related treatments.
Looking for dosing and water-care advice? Visit the Fish Antibiotics Blog for practical guides and treatment tips.
