Betta Fish Fin Rot: Fin Loss, Symptoms, Causes & Treatment

Have your betta’s fins started to look ragged, frayed, or discolored? Don’t panic—fin rot is a common issue and one that’s completely treatable with the right steps. In this guide, you’ll learn how to identify fin rot, what causes it, the best treatment options for each severity level, and how to prevent it from coming back.

What Is Fin Rot?

Fin rot is a bacterial infection (often with a secondary fungal component) that causes a betta’s fins to become ragged, discolored, and eventually deteriorate. It usually develops due to poor water quality, stress, or injury, all of which weaken your betta’s immune system.

For help distinguishing between fin rot and simple fin loss, check out our comparison guide: Betta Fin Rot vs. Fin Loss

Symptoms of Fin Rot

Early signs:

• Frayed or ragged fin edges
• Discoloration (white, black, or red on the fin tips)
• Transparent or “melted” appearance

Moderate to severe signs:

• Holes in the fins or missing sections
• Inflamed or slimy base of the fins
• Lethargy, hiding, or appetite loss

What Causes Fin Rot?

• Poor Water Quality: Ammonia and nitrite spikes and an unclean tank environment promote the bacteria and fungi that cause fin rot. Use test strips to check water levels regularly. Learn more in our full guide on Ideal Betta Water Parameters
• Stress: Aggressive tank mates, sudden temperature changes, or overcrowding can lower immunity.
• Injury: Sharp decor or strong filters can tear fins, creating an entry point for infection.

How to Treat Fin Rot in Betta Fish

🔹 Mild Fin Rot (Early Stage)

Use Aquarium Salt

1. Get water test kit
2. Lower water temp to ~75°F to slow bacterial growth (but not below 74°F).
3. Use a 1 tsp of aquarium salt per gallon (pre-dissolve in a separate cup).
4. Perform 90% water changes daily.
5. Repeat for up to 10 days. Discontinue if betta shows stress or if no improvement occurs.

🔹 Moderate Fin Rot

Use API Melafix

• Contains tea tree extract to heal damaged fins.
• Dose daily for 7 days.
• Combine with aquarium salt for better results.
• Ideal for bacterial infections and open wounds.

🔹 Severe Fin Rot / Body Rot

Use Stronger Medication (Maracyn + Maracyn 2)

• Do a 90% water change.
• Mix half the recommended dose of each product.
• Dose every 3 days for 9 days.
• If no change, pause for 4–5 days before trying again.
• Get the Betta Fish Guide Book

📅 Healing Timeline: What to Expect

• Days 1–3: Rot stops spreading
• Days 4–7: Appetite returns, fins may regain color
• Days 7–14: Fins begin regrowing (often clear at first)
• 2–4 weeks: Nearly full recovery in clean, stable tank conditions

🧱 Preventing Fin Rot from Coming Back

• Test water weekly and maintain ammonia/nitrites at 0 ppm
• Keep your tank between 78–81°F
• Use a filter with a gentle flow
• Smooth or replace sharp decorations
• Perform 25–50% weekly water changes
• Consider Indian almond leaves for natural antibacterial support
• Quarantine new fish or plants before adding to your main tank
• Ensure your setup meets proper standards. Read our full Betta Fish Tank Guide for tips on ideal tank size, equipment, and setup.

❓ Frequently Asked Questions

Is fin rot contagious?

Not directly, but poor water quality can affect all fish in the tank, making them more susceptible to infections like fin rot.

Will my betta’s fins grow back?

Yes, with proper care and clean water, your betta’s fins typically regrow within a few weeks. New fin growth often appears clear or slightly translucent.