Fast Aquatics

Two organisms, similar disease

Freshwater ich: Ichthyophthirius multifiliis - protozoan parasite, embedded in fish tissue under a blister, falls off and reproduces in substrate.

Saltwater ich: Cryptocaryon irritans - functionally similar life cycle but a different organism. Treatment differs.

Both produce small white spots (1-2mm) on fish body and fins, flashing/scratching behavior, rapid breathing if gills affected. Untreated, mortality is high - especially in saltwater.

Life cycle (the critical knowledge)

  1. Trophont stage: parasite embedded in fish tissue, visible as white spot. Cannot be killed by medication while in this phase
  2. Tomont stage: parasite drops off fish, falls to substrate, encysts
  3. Tomite stage: tomont divides into hundreds of swimming theronts that hunt new fish hosts
  4. Theront infects new fish: cycle repeats

The full cycle is 14-28 days at 78F (faster at higher temps). Treatment must outlast the cycle to break it.

Freshwater ich treatment

Heat method (preferred)

  1. Raise tank temperature to 86F (slowly, over 24 hours)
  2. Maintain 86F for 14 days
  3. Increase aeration (heated water holds less oxygen)
  4. Heat speeds the parasite life cycle so the trophont detaches faster, then dies during free-swimming stage when out of host

Salt + heat (more aggressive)

Add aquarium salt at 1 tablespoon per 5 gallons + raise temp to 86F. Effective for most freshwater fish. Note: salt-sensitive species (Corydoras, scaleless catfish, plants) tolerate this poorly.

Medication (worst case)

API Super Ick Cure, Kordon Rid Ich+, or formalin/malachite green products. Effective but harsh on biofilter and inverts.

Saltwater ich treatment

Marine ich is harder to eradicate than freshwater. Three proven methods:

Copper (Cupramine, Coppersafe)

  1. Move fish to a fishless QT tank (no substrate, no live rock - copper kills inverts and bacteria)
  2. Dose copper to therapeutic level (0.5 ppm Cupramine, 1.5-2.0 ppm Coppersafe)
  3. Maintain copper level for 14-21 days, testing daily
  4. Display tank goes fallow (no fish) for 76 days minimum to ensure all parasites die without hosts
  5. Return fish to display after fallow period

Copper is the most reliable saltwater ich treatment. Limitations: kills coral, inverts, snails, shrimp - cannot use in display.

Tank-transfer method (TTM)

For copper-sensitive fish (angels, mandarins, butterflies):

  1. Two QT tanks fully cycled, one in use
  2. Move fish to fresh QT every 72 hours, restart drained one
  3. 3 transfers (Day 1, 4, 7, 10, 13) breaks the cycle
  4. Trophonts detach in transfer tank, fish moves on, tomonts can't reach a host

Hyposalinity

  1. Reduce salinity in QT to 1.009 SG over 48-72 hours (slowly)
  2. Maintain hyposalinity for 4 weeks
  3. Slowly raise back to 1.024-1.026 over 7 days

Effective on Cryptocaryon. Easier on fish than copper but harder to maintain stable salinity.

What does NOT work

  • Garlic in food: appetite booster only, no parasiticidal effect
  • UV sterilizers: kill some free-swimming theronts but don't break cycle alone
  • "Reef-safe" ich treatments: mostly ineffective; if it doesn't kill inverts, it doesn't kill ich at therapeutic dose
  • Cleaner shrimp / cleaner gobies: they don't actually cure ich
  • "Ride it out" for healthy fish: ich in a reef tank is forever; healthy-looking fish are still infected and contagious

Prevention is the answer

The vast majority of ich outbreaks trace to a single new fish added without quarantine. Quarantine every new saltwater fish for 30 days minimum with prophylactic copper. The 30 days you wait save you 76+ days of fallow display tank later.