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Fungal Infection (Saprolegnia)

moderate severityfungalfreshwater & saltwater10-day treatment

True fungal infections appear as white cottony growths, usually on damaged tissue. Unlike bacterial columnaris (which looks similar), true fungus has a fuzzy, branching appearance under magnification. Often a secondary infection after injury.

Key Symptoms

White cotton-like tufts on body, fins, or mouthGray/white fuzzy patchesUsually appears on wounds or damaged tissue firstLethargy
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Symptoms to Watch For

  • White cotton-like tufts on body, fins, or mouth
  • Gray/white fuzzy patches
  • Usually appears on wounds or damaged tissue first
  • Lethargy

Common Causes

  • Saprolegnia or Achlya fungi
  • Secondary infection on damaged/stressed tissue
  • Poor water quality
  • Low temperature stress

Treatment Protocol for Fungal Infection (Saprolegnia)

Treat with Ich-X (contains malachite green + formaldehyde) — effective against fungi. API Pimafix is a milder option. Methylene blue baths work for eggs with fungus. Remove visibly affected tissue gently if possible. Improve water conditions.

How to Identify This Condition

Look for these symptoms in your fish:

  • White cotton-like tufts on body, fins, or mouth
  • Gray/white fuzzy patches
  • Usually appears on wounds or damaged tissue first
  • Lethargy

Early detection is critical — the sooner you begin treatment, the better the prognosis. Observe your fish daily during routine feeding for any behavioral or physical changes.

Root Causes

Understanding what caused the problem helps you prevent recurrence:

  • Saprolegnia or Achlya fungi
  • Secondary infection on damaged/stressed tissue
  • Poor water quality
  • Low temperature stress

Recommended Medications

The following medications are effective against Fungal Infection (Saprolegnia):

  • Ich-X — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • API Pimafix — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • Methylene blue — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • SeaChem PolyGuard — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.

Always have these medications on hand before you need them. See our quarantine tank guide for proper treatment setup.

Water Quality During Treatment

Maintain pristine water conditions during treatment. Perform 25% daily water changes using Seachem Prime as your water conditioner. Remove activated carbon from your filter during medication (carbon absorbs medications). Increase aeration with an air stone — sick fish need extra oxygen. Monitor ammonia and nitrite daily with your test kit.

Recovery & Quarantine

With proper treatment, most fish recover within 10 days. Continue treatment for the full course even if symptoms resolve early. Reintroduce treated fish to the main tank gradually, and observe for 7 additional days.

Prevention

The best treatment is prevention. Follow these practices to reduce the risk:

  • Maintain warm, clean water
  • Treat injuries promptly to prevent secondary fungal infection
  • Remove dead eggs from spawning tanks
  • Avoid overcrowding and aggression

For a complete prevention strategy, read our quarantine tank guide and maintenance schedule.

Medications & Treatments

💊 Ich-X💊 API Pimafix💊 Methylene blue💊 SeaChem PolyGuard

Prevention Checklist

  • Maintain warm, clean water
  • Treat injuries promptly to prevent secondary fungal infection
  • Remove dead eggs from spawning tanks
  • Avoid overcrowding and aggression
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