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Internal Parasites (Wasting Disease)

moderate severityparasiticfreshwater & saltwater21-day treatment

Internal parasites cause chronic wasting — fish eat but slowly lose weight. White stringy feces is the classic sign. Multiple types of parasites can be involved, often requiring combination treatment.

Key Symptoms

Weight loss despite eating wellWhite stringy fecesBloatingLoss of colorHiding and lethargy
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Symptoms to Watch For

  • Weight loss despite eating well
  • White stringy feces
  • Bloating
  • Loss of color
  • Hiding and lethargy

Common Causes

  • Various internal parasites (nematodes, tapeworms, hexamita)
  • Introduced via infected fish or live food
  • Stress activating dormant parasites

Treatment Protocol for Internal Parasites (Wasting Disease)

Treat with combination of Metroplex (metronidazole) for flagellates + General Cure (metronidazole + praziquantel) for worms. Feed medicated food using Seachem Focus as binder. Treat for 2 weeks minimum. Levamisole for stubborn nematodes.

How to Identify This Condition

Look for these symptoms in your fish:

  • Weight loss despite eating well
  • White stringy feces
  • Bloating
  • Loss of color
  • Hiding and 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:

  • Various internal parasites (nematodes, tapeworms, hexamita)
  • Introduced via infected fish or live food
  • Stress activating dormant parasites

Recommended Medications

The following medications are effective against Internal Parasites (Wasting Disease):

  • API General Cure — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • Seachem Metroplex — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • Levamisole — follow manufacturer dosing instructions. Treat in a hospital/quarantine tank when possible to avoid disrupting your main tank's biological filtration.
  • Fritz Expel-P — 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 21 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:

  • Quarantine and deworm new fish
  • Avoid wild-caught live food
  • Maintain clean substrate
  • Regular observation of fish behavior and feces

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

Medications & Treatments

💊 API General Cure💊 Seachem Metroplex💊 Levamisole💊 Fritz Expel-P

Prevention Checklist

  • Quarantine and deworm new fish
  • Avoid wild-caught live food
  • Maintain clean substrate
  • Regular observation of fish behavior and feces
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