API Fin and Body Cure is an over-the-counter aquarium antibiotic containing doxycycline hyclate, a tetracycline-class antibiotic. It is formulated to treat bacterial infections that affect both the fins and body of freshwater fish, including fin rot, body ulcers, and popeye. Doxycycline has broad-spectrum activity against many gram-positive and gram-negative bacteria and has been a dependable hobbyist antibiotic for decades. API Fin and Body Cure is an OTC aquarium product, not a prescription-grade veterinary medication. Availability of aquarium antibiotics has been affected by FDA enforcement actions, so status varies by region. For valuable fish, consult an aquatic veterinarian.
Overview
Doxycycline binds to the bacterial ribosome and inhibits protein synthesis. It is well absorbed from aquarium water, penetrates tissues well, and is effective against many of the bacterial pathogens commonly encountered in freshwater aquariums. Fin and Body Cure combines doxycycline with other supporting ingredients to treat infections that affect both external fin tissue and deeper body wounds.
Uses
- Bacterial fin rot
- Body ulcers and skin lesions
- Popeye (bacterial form)
- Bacterial hemorrhagic septicemia
- Secondary bacterial infection following parasitic disease
- Early columnaris in some cases
Dosage
- Water dosing: 1 packet per 10 gallons of water
- Duration: One dose every 48 hours, with a 25% water change before each dose. Typical treatment is 4 days (two doses) but can be extended.
Always follow the product label for exact dosing.
Safety Considerations
- Freshwater use — Labeled for freshwater aquariums
- Scaleless fish — Generally tolerated at standard dose; monitor closely
- Invertebrates — Not recommended for invertebrate tanks; shrimp and snails may be sensitive
- Plants — Can affect some sensitive plant species; most hardy plants tolerate label doses
- Biological filter — Doxycycline can have some effect on nitrifying bacteria. Monitor ammonia and nitrite during and after treatment.
- Water staining — Mild yellowing of water during treatment is normal and clears with water changes and carbon
- User safety — Wash hands after handling. Do not use if pregnant or if you have a doxycycline allergy.
- Regulatory status — Availability as an OTC aquarium product has been affected by FDA enforcement actions
Water Chemistry Effects
- Minor yellowing of water during treatment
- Minimal direct effect on pH or hardness
- Activated carbon removes doxycycline — remove carbon during treatment
- Some effect on beneficial bacteria; monitor parameters carefully
How to Use
- Test water parameters and perform a water change if needed
- Remove activated carbon from the filter
- Dissolve one packet per 10 gallons
- Repeat dose every 48 hours with a 25% water change before each new dose
- Complete the full treatment course
- Monitor ammonia and nitrite during treatment
- After treatment, perform a 25% water change and return activated carbon
FAQs
What kind of antibiotic is this? API Fin and Body Cure is doxycycline-based, a tetracycline-class antibiotic with broad-spectrum activity.
Is it safe for invertebrates? No, shrimp and snails may be sensitive. Use in a hospital tank without invertebrates.
Can I use it in saltwater? It is labeled for freshwater use. Marine use should be guided by an aquatic veterinarian.
Will it kill my plants? Hardy plants generally tolerate label doses; sensitive species may show mild stress.
How is it different from Furan-2? Fin and Body Cure is doxycycline-based while Furan-2 is nitrofuran-based. They cover overlapping but not identical bacterial spectrums.
Do I need a prescription? Availability of aquarium antibiotics has been affected by FDA enforcement actions. Check current status in your region.