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Fix Sulfa (Fish Sulfa Forte) Tablets, 960 mg
Fix Sulfa at a Glance
For
Ornamental aquarium fish (freshwater and saltwater)
Helps With
Fin and tail rot, ulcers, columnaris, pop-eye, and other bacterial signs
Form
Scored tablets, 960 mg each
Count Sizes
30 count, 60 count
Water Type
Freshwater and saltwater
Made In
United States by Aqua Soma Labs
Fix Sulfa (SMZ/TMP 960 mg) is an antibacterial treatment for ornamental aquarium fish. Each scored tablet pairs sulfamethoxazole 800 mg with trimethoprim 160 mg, and aquarists use it to help manage suspected bacterial problems in freshwater and saltwater aquariums.
In older hobby listings and aquarium forums, this SMZ/TMP product also goes by Fish Sulfa, Fish Sulfa Forte, FISHBIOTIC SMZ/TMP, and Aqua Sulfa. Fix Sulfa is the current-production replacement for the discontinued Thomas Labs Fish Sulfa Forte. Aquarists use this combination for fin and tail rot, columnaris (often presenting as cotton wool disease), skin sores and ulcer-like lesions, bacterial hemorrhagic septicemia, pop-eye (exophthalmia), cloudy eyes, and body slime issues linked to certain bacteria such as Aeromonas, Vibrio, or Streptococcus.
SMZ/TMP pairs two ingredients that work together to help slow the growth of certain bacteria. Used as directed for fish, sulfamethoxazole and trimethoprim work best alongside stable water parameters, strong aeration, and good husbandry. Fix Sulfa is the current-production version.
Fix Sulfa comes as a consistent 960 mg tablet that is easy to crush and dissolve. You can buy it online in bottles of 30 or 60 tablets with fresh expiration dates, so you can match the amount to a single quarantine tank or a multi-tank fish room.
Start treatment at the first signs of bacterial stress, and treat affected fish in a hospital or quarantine tank whenever possible. Watch for the symptoms below.
Fish Symptoms Aquarists Treat With Fix Sulfa
Fin and tail rot (frayed or rotting fins)
Skin sores, ulcer-like lesions, and red streaks
Pop-eye (bulging eyes) and cloudy eyes
Columnaris, often with a cotton wool look
Bacterial hemorrhagic septicemia and body slime issues
Lethargy, rapid breathing, or loss of appetite that clean water does not fix
Order before 1:30 p.m. CT, Monday through Friday, for same-day dispatch. Fix Sulfa ships from our U.S. warehouse via USPS or UPS.
Important Notice: This product is intended for aquarium and ornamental fish only. It is not for animals used for food.
Fish Sulfa Forte vs Fix Sulfa: What Changed?
If you previously purchased Thomas Labs Fish Sulfa Forte, FISHBIOTIC SMZ/TMP or Aqua Sulfa, here is what has changed and what remains the same:
Same Active Ingredients Fix Sulfa contains sulfamethoxazole 800 mg and trimethoprim 160 mg per tablet (SMZ/TMP 960 mg), the same dual-ingredient formula found in legacy products like Thomas Labs Fish Sulfa Forte, FISHBIOTIC SMZ/TMP, and Aqua Sulfa.
Updated Branding Aqua Soma Labs makes Fix Sulfa as a current-production replacement for the discontinued Thomas Labs Fish Sulfa Forte and other legacy SMZ/TMP fish treatments. The active ingredients and intended use are the same.
Same Tablet Form Each tablet delivers a consistent 960 mg in a format that is easy to crush and dissolve for aquarium use, following the same scored-tablet approach aquarists are familiar with from Fish Sulfa Forte.
Flexible Bottle Sizes Available in 30-count and 60-count bottles with fresh expiration dates, giving hobbyists options for short treatments, quarantine setups, or multi-tank fish rooms.
Benefits of Fix Sulfa for Fish
Dual-Action SMZ/TMP Combination
Fix Sulfa pairs sulfamethoxazole and trimethoprim (SMZ/TMP), a combination aquarists use to help manage certain bacterial issues in ornamental fish when used as directed.
Made in the United States
Fix Sulfa is made in the United States by Aqua Soma Labs as the current-production version of the discontinued Fish Sulfa Forte, with fresh expiration dates on every bottle.
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, cotton wool disease, ulcer-like lesions, pop-eye, and other persistent bacterial signs in ornamental freshwater and saltwater fish.
Helps With External and Internal Signs of Bacterial Stress
SMZ/TMP tablets are often used in a hospital tank for visible skin sores, fin damage, and hemorrhagic septicemia, and in situations where fish show lethargy or reduced appetite alongside water-quality corrections and supportive care.
Consistent 960 mg Tablet Strength
Each tablet provides a consistent 960 mg format, making it easier to plan repeatable amounts across different tank sizes. Available in 30- or 60-tablet bottles.
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 amounts.
Helpful for Quarantine and Hospital Tanks
Treating in a separate hospital or quarantine tank can help you observe fish more closely, control the amount more precisely, and reduce unnecessary exposure for healthy tank mates during treatment.
Usage Guidelines & Instructions
These steps follow the Fix Sulfa 960 bottle label directions for SMZ/TMP use in ornamental aquarium fish.
Quick Usage Summary: 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:
Measure Water Volume
Calculate actual water volume (account for substrate, decor, and fill level).
Use a Hospital Tank
Use a hospital/quarantine tank when possible for better control and observation.
Remove Carbon and UV
Remove activated carbon and other chemical media; turn off UV sterilizers during treatment.
Boost Aeration
Increase aeration and surface agitation; keep temperature stable.
Directions for Use:
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. Add one tablet per 40 gallons (151 L) of water to be treated.
Repeat Every 24 Hours
Repeat every 24 hours. Perform a partial water change between treatments throughout the treatment.
Complete the Treatment 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.
Post-Treatment Clean Up
After the treatment 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.
Fix Sulfa Amounts by Aquarium Size
Tank volume
Fix Sulfa 960 amount
How to measure
10 gallons (38 L)
1/4 tablet
Split a scored tablet, or add 1/4 of one dissolved tablet
20 gallons (76 L)
1/2 tablet
Split a scored tablet, or add 1/2 of one dissolved tablet
40 gallons (151 L)
1 tablet (label standard)
Dissolve one whole tablet
80 gallons (303 L)
2 tablets
Dissolve two whole tablets
120 gallons (454 L)
3 tablets
Dissolve three whole tablets
The Fix Sulfa 960 label states one (1) dose (one tablet) per 40 gallons (151 L), which is about 24 mg of combined sulfamethoxazole and trimethoprim per gallon. The 40-gallon row is the exact label instruction; the other rows scale that same rate. For tanks under 40 gallons you can split a scored tablet, or dissolve one tablet in a measured cup of tank water and add the matching fraction for more accuracy. Dose by your treatment tank's water volume, not the number of fish, repeat once every 24 hours for 5 to 10 days, and follow the bottle label or your aquatic veterinarian over this quick-reference chart.
What to Expect During Treatment
Days 1 to 2
Fish 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.
Days 3 to 5
Watch 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 veterinarian.
Days 5 to 10
Even if the fish are improving, finish all the recommended days so the infection does not return. Afterward, run a partial water change and put activated carbon back in to clear any leftover product.
What You Need for a 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 keep tabs on water quality.
A dechlorinator for the water changes between doses.
A small net and a clean cup for gentle transfer and measuring the dose.
Pro Tip: Hospital tank treatment helps protect the display aquarium, keeps the amount consistent, and makes it easier to keep ammonia and nitrite at 0 during recovery.
How Fix Sulfa Works
Each Fix Sulfa tablet pairs sulfamethoxazole 800 mg and trimethoprim 160 mg (SMZ/TMP). Dissolved and added to aquarium water as directed, the two ingredients work together to help slow the growth of certain bacteria.
Alongside the active ingredients, each tablet includes standard ingredients that hold the tablet together and help it disperse properly in water. Aquarists use Fix Sulfa for fin and tail rot, ulcer-like lesions, columnaris, pop-eye, and other bacterial signs in ornamental freshwater and saltwater fish.
Safety and Tank Notes
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 treatment.
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.
Stop Treatment If
Fish show severe stress, rapid gill movement, gasping at the surface, loss of balance, or worsening symptoms. Increase aeration immediately and consult an aquatic veterinarian if signs do not stabilize.
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.
Filtration During Treatment
Remove activated carbon and other chemical filtration media before dosing. Turn off UV sterilizers during treatment. Resume normal filtration after the treatment is complete.
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.
Important Warnings & Precautions
Aquarium Use Only
Fix Sulfa is intended for ornamental aquarium fish only. It is not for animals raised for food.
Not for Food Fish
Do not use on fish raised for food. This product is made and labeled as an antibacterial treatment for ornamental aquarium fish only.
Handling Note
Avoid contact with the dissolved product, wash your hands after handling, and wear gloves if needed. Keep the tablet contents and dissolved product off skin and out of eyes.
Keep Out of Reach
Store Fix Sulfa out of reach of children and pets. Use it only as directed on the product label.
Storage
Keep the container tightly closed and store in a cool, dry place, away from direct sunlight and moisture. Check the expiration date and do not use tablets past it.
Discontinue If No Improvement
If no improvement is noted after 5 days of treatment, discontinue use as stated on the label and re-evaluate the diagnosis or seek aquatic veterinary advice.
Do Not Mix Treatments
Avoid combining Fix Sulfa with other treatments unless the product label explicitly allows it or an aquatic veterinarian advises it.
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 Sulfa used for?
Fix Sulfa (SMZ/TMP) is used by aquarists to help manage certain 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, pop-eye, and other persistent bacterial signs.
What is fish sulfa forte?
Fish Sulfa Forte was a Thomas Labs SMZ/TMP treatment (sulfamethoxazole and trimethoprim) for ornamental aquarium fish. Thomas Labs discontinued it, and Fix Sulfa by Aqua Soma Labs is the current-production version with the same two active ingredients in a 960 mg tablet.
What is the difference between Fish Sulfa Forte and Fix Sulfa?
Fish Sulfa Forte (Thomas Labs), FISHBIOTIC SMZ/TMP, and Aqua Sulfa are older SMZ/TMP fish brands. Thomas Labs discontinued Fish Sulfa Forte, and Fix Sulfa by Aqua Soma Labs is the current-production version. It contains the same two active ingredients (sulfamethoxazole 800 mg and trimethoprim 160 mg) in the same 960 mg tablet format.
Is Fix Sulfa a replacement for Aqua-SMZ/TMP?
Yes. If you previously purchased Aqua-SMZ/TMP or similar legacy SMZ/TMP products for ornamental fish, Fix Sulfa provides the same active ingredient combination (sulfamethoxazole and trimethoprim, 960 mg per tablet) under updated branding from Aqua Soma Labs.
Where can I buy SMZ/TMP fish tablets online?
You can buy Fix Sulfa (SMZ/TMP 960 mg) directly from Fine Pet Health. Orders placed before 1:30 p.m. CT (Mon-Fri) typically ship the same business day from our U.S. warehouse.
What are the active ingredients in each Fix Sulfa tablet?
Each tablet contains sulfamethoxazole 800 mg and trimethoprim 160 mg (SMZ/TMP).
What is the Fix Sulfa amount for fish?
Follow your bottle label directions. The Fix Sulfa 960 label says to 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.
How much Fix Sulfa should I use per gallon?
The Fix Sulfa 960 label directs one (1) dose (one tablet) per 40 gallons (151 L) of water to be treated. Dissolve the dose, add it to the treatment tank, and repeat every 24 hours with a partial water change between doses for 5-10 days. Measure the tank volume first.
How long should I treat with Fix Sulfa?
For fish, the Fix Sulfa 960 label directs treatment for 5-10 days, dosing once every 24 hours with a partial water change between treatments. Discontinue use if no improvement is noted after 5 days, then re-check water quality and the likely cause before continuing.
How soon should I see improvement with Fix Sulfa?
Many aquarists watch for early signs by days 3 to 5: 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, discontinue use and consult an aquatic veterinarian.
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 treatments from water, and UV sterilizers may reduce treatment availability. Remove carbon/chemical media and turn off UV during treatment, then resume normal filtration after the treatment is complete.
Will Fix Sulfa harm beneficial bacteria in the aquarium?
Any antibacterial 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.
Can Fix Sulfa treat fungal, viral, or parasitic infections?
Fix Sulfa (SMZ/TMP) is an antibacterial treatment intended for certain 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.
Is Fix Sulfa safe for betta fish and small aquariums?
Bettas and other small-tank fish can be treated with Fix Sulfa, but accurate dosing is especially important in smaller volumes. Measure your actual water volume carefully and use a hospital container for best results. Monitor closely for any signs of stress.
Does Fix Sulfa work in saltwater aquariums?
SMZ/TMP tablets can be used in saltwater setups when treating ornamental fish. If your system includes corals, invertebrates, or a refugium, treat fish in a separate hospital or quarantine tank to reduce risk to the display ecosystem.
Can I combine Fix Sulfa with other fish treatments?
Avoid combining Fix Sulfa with other treatments unless the product label explicitly allows it or an aquatic veterinarian advises it. Mixing treatments can increase stress on fish and make it harder to identify what is working.
What if my fish are not improving after treatment?
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.
What should I do after finishing Fix Sulfa treatment?
After the recommended days are complete, run a partial water change and resume normal filtration. Put activated carbon back in to clear any leftover product, and keep monitoring ammonia and nitrite for several days to confirm the tank is stable.
How should I store and dispose of 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. For disposal, follow your local guidance for safe household disposal.
Bottom Line
Fix Sulfa is an SMZ/TMP 960 mg antibacterial treatment (sulfamethoxazole 800 mg plus trimethoprim 160 mg) for bacterial problems in ornamental aquarium fish. It is the current-production replacement for the discontinued Thomas Labs Fish Sulfa Forte. Dose by water volume at one tablet per 40 gallons (151 L), treat for 5 to 10 days in a hospital tank with a partial water change between doses, and reassess at day 5. It will not help with fungal, viral, or parasitic problems, and it is for ornamental aquarium fish only, not for animals raised for food. If you are unsure whether the cause is bacterial, talk to an aquatic veterinarian first.
Ready to start? Choose the bottle size that fits your setup above, or compare the rest of the Fix line below.
More Fish & Bird Treatments
Fix Mox (Amoxicillin) 250/500mg A treatment for fin rot, dropsy, ulcers, and other bacterial infections in ornamental fish. Available in 30-count and 100-count capsules. Shop Fix Mox
Fix Zole (Metronidazole) 250/500mg Targets anaerobic bacteria and protozoa including Hexamita and hole-in-the-head disease in ornamental fish. Available in 60-count bottles. Shop Fix Zole
Fix Doxy (Doxycycline) 100mg A treatment for columnaris, respiratory infections, and Mycoplasma in ornamental fish and non-food pet 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 ornamental fish and non-food pet birds. Available in 12-count and 30-count tablets. Shop Fix Zithro
Fix Cin (Clindamycin) 150mg A treatment for bacterial skin and soft tissue concerns in ornamental fish. Shop Fix Cin
Fix Pen (Penicillin) 500mg A penicillin treatment for 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 non-food pet birds. Shop Fix Flex
Fix Flox (Ciprofloxacin) 500mg A treatment for bacterial infections including fin rot, ulcers, columnaris, and septicemia in ornamental fish and non-food pet birds. Shop Fix Flox
Guides and care tips Visit the Fish & Bird Care Blog for practical usage guides, water-care advice, and treatment tips.
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Tried to order fish meds through the other guy, but their web site wouldn't work, so I tried fine pets, it was fast, easy, and no problems, definitely got my business from now on.
Hi Daniel, we really appreciate the awesome review! It’s great to hear that ordering your Fix Sulfa with us was a breeze after having trouble elsewhere. Thanks for choosing us, and we can't wait to see you for your next order!
D
David McConnaughey (Las Vegas, NV)
Fix Sulfa (SMZ/TMP) 960mg 30/60ct Fish Antibiotic
Dear David, thank you immensely for leaving a 5-star review for your recent Fix Sulfa purchase! We are so glad to see that you are fully satisfied with your order. Your support is incredibly valuable to us, and we can't wait to assist you again the next time you need to restock!
J
Janice Amelunk (Jamestown, TN)
Product as described
Would buy from again!
J
Jackie Eaten (Chickamauga, GA)
Fast an accurate
Very fast service an always accurate
A
Amy Patterson (Jacksonville, FL)
Aqua-SMZ/TMP
Item made it on time, and solved my fish bacterial problem.
