Description
Fish Sulfa Forte (Fix Sulfa) is a combination tablet for freshwater and saltwater aquarium fish: 800 mg sulfamethoxazole plus 160 mg trimethoprim, 960 mg in total, made by Aqua Soma Labs. One tablet treats 40 gallons, added daily for 5 to 10 days per the label.
- Active ingredients
- Sulfamethoxazole 800 mg and trimethoprim 160 mg (SMZ/TMP)
- Strength
- 960 mg per tablet
- Bottle sizes
- 30 or 60 tablets
- Label dose
- 1 tablet per 40 gal (151 L)
- Course
- Once a day for 5 to 10 days; stop if no improvement after day 5
- Made by
- Aqua Soma Labs, USA
Why two ingredients in one tablet
Bacteria need folate to grow, and they make it in several steps. Sulfamethoxazole blocks one step and trimethoprim blocks the next. Together they work far better than either alone, and the pair covers both gram-positive and gram-negative bacteria. Aquarists use Fish Sulfa Forte for:
- Red, ulcerated sores of the kind linked to Aeromonas and Pseudomonas
- Columnaris-type patches on the body and around the mouth
- Fin rot that has reached the fin base
- Popeye and cloudy eyes with a suspected bacterial cause
- Treating large hospital tanks economically, since one tablet covers 40 gallons
As with every antibacterial, it does nothing against ich, velvet, flukes, or fungus. Internal flagellates and hole-in-the-head need Fish Zole.
Fish Sulfa Forte dosage by tank size
This is the outlier in the Fix line. Most products are dosed per 10 to 20 gallons; Fix Sulfa is dosed per 40.
| Tank | Liters | 960 mg tablets per day |
|---|---|---|
| 10 gal | 38 L | ¼ |
| 20 gal | 76 L | ½ |
| 40 gal | 151 L | 1 |
| 80 gal | 303 L | 2 |
| 120 gal | 454 L | 3 |
| 200 gal | 757 L | 5 |
For tanks under 40 gallons, dissolve one whole tablet in 4 measured cups of tank water. Each cup then equals the dose for 10 gallons. Keep the rest covered and use it the same day only. The label on your bottle takes priority over this chart.
Running a course of Fish Sulfa Forte
- Prepare the hospital tank. Dechlorinated water at matching temperature, a sponge filter, and an air stone.
- Take out absorbers. Carbon, chemical media, and UV all reduce the dose, so remove them until the end.
- Dissolve the tablet completely. Crush it and stir it into tank water before adding. Undissolved pieces dose unevenly.
- Repeat each day. Change part of the water, then add a fresh full dose for the tank's volume.
- Assess on day 5. Sores should stop spreading and look less red. If they don't, stop as the label directs.
- Finish well. Continue up to day 10 while the fish improve, then change a large share of water and run fresh carbon.
Cost per course
Because of the 40-gallon dose, Fish Sulfa Forte is one of the cheapest courses in the line for large tanks. A 10-day course in a 40 gallon tank uses 10 tablets, about $9.30 from the 60-count bottle at list price. In a 20 gallon tank the same course uses 5 tablets. The 30-count bottle covers three courses in 40 gallons; the 60-count suits tanks of 80 gallons and up.
Fish Sulfa Forte next to the rest
| Product | Label dose | Coverage | Strong point |
|---|---|---|---|
| Fish Sulfa Forte | 1 tablet per 40 gal | Gram-positive and gram-negative | Ulcers and columnaris-type cases, big tanks |
| Fish Flox | 1 capsule per 10 gal | Mostly gram-negative | The most aggressive ulcers |
| Fish Doxy | 1 tablet per 15 gal | Broad | Gill infections, relapsing fin rot |
| Fish Mox | 250 mg per 10 gal | Gram-positive, some gram-negative | Milder, early cases |
Compare every Fix product on our fish antibacterials page.
Things to watch
- Test ammonia and nitrite daily; the biofilter can slow down during treatment.
- Keep invertebrates and corals out of the treated water.
- Sulfamethoxazole doesn't dissolve easily. Crush the tablet finely and stir it into tank-temperature water.
- Don't combine Fish Sulfa Forte with other treatments unless an aquatic veterinarian advises it.
- Store tablets sealed and dry, away from children and pets. Don't flush leftovers.
Fish Sulfa Forte questions
Fix Sulfa or Fish Sulfa Forte?
Fish Sulfa Forte is the name aquarists search for sulfamethoxazole and trimethoprim tablets for fish. Fix Sulfa is the Aqua Soma Labs 960 mg tablet, so both names appear here.
What does SMZ/TMP mean?
It's short for sulfamethoxazole and trimethoprim, the two ingredients in each tablet.
Why is the dose per 40 gallons when other products are per 10?
That's the rate Aqua Soma Labs sets for this 960 mg combination tablet. Follow the 40-gallon rule for Fix Sulfa only, and never carry it over to other products.
Can I use it in saltwater?
Yes, the label covers freshwater and saltwater ornamental fish. Keep reef invertebrates out of the treatment tank.
Where can I buy fish sulfa?
Local stock is rare and names vary between sellers. We carry Fix Sulfa 960 mg in 30 and 60 count and ship from Missouri the same or next business day.
For aquarium and ornamental fish only.
