Cause

• "Ick" is shorthand for the Ichthyophthirius parasite, which is often present in aquariums at pet stores and fish dealers. Ick typically attacks weakened or stressed fish during shipment to the store, then spreads to home aquaria as hobbyists unwittingly buy the infected fish.
  
  The Ick parasite has a cyclical lifestyle, meaning it infects the fish to grow to maturity, then leaves to fish to reproduce. After the initial infection characterized by tiny white spots on a fish's skin and fins, the parasite exits the fish, leaving it vulnerable to secondary fungal infections. The parasite reproduces by creating a cyst, often visible on the tank floor. The cyst later bursts and distributes new adult parasites to infect more fish.
  
  

Freshwater vs. Marine Ick

• Ick attacks both freshwater and marine species. In freshwater aquaria, the Ichthyophthirius organism is the culprit; in marine environments, the Cryptocaryon parasite causes a disorder equivalent to freshwater Ick.
  
  

Diagnosis

• Freshwater and marine Ick causes tiny (1mm diameter) white spots to appear on the infected fish's skin and fins. The spots are visible to the naked eye. An infected fish may also breathe heavily and make rapid gill movements if the disease is advanced.
  
  

Treatment

• When the parasite is in the fish or in the cyst stage, the infection is resistant to treatment. The best time to cure the infection is before the cyst forms or after it bursts. Many aquarium dealers sell small squirt bottles of copper-based medications with the active ingredient copper sulfate or "soluble copper salts," which present the easiest way to cure Ick. Malachite Green is another highly effective treatment for Ick and fungal infections. Always read the label carefully and use medications as directed.
  
  

Treatment Procedure

• When using commercial Ick treatments, read the label for special application instructions, dosages and warnings. For freshwater tanks, perform a water change and vacuum the gravel, as organic wastes can reduce the effectiveness of the medication. Keep good aeration and water movement throughout the course of treatment, but remember to remove the activated charcoal or carbon from the aquarium filter so the medication will not be filtered out. Perform the full course of treatment---even if it seems like the fish are cured, the free-swimming parasites will still need to be eliminated.
  
  In marine tanks, remove the filter carbon, any live plants and invertebrates (such as sea anemones, which have porous outer skin) before administering medication, and always follow the instructions exactly.
  
  

Prevention

• Maintaining a healthy tank greatly reduces the chance of an Ick outbreak. Keep the filtration and aeration systems in top-notch condition. Don't overfeed the fish; uneaten food clogs filters and upsets the chemical balance of the water. Quarantine newly-purchased fish for two weeks in a separate tank prior to introducing them to the main tank. If you don't have a separate quarantine tank, acclimate the new fish by floating its plastic bag in the aquarium for 20 minutes, then gently pick the fish out the bag with a net and add it to the aquarium. Never dump the water from the bag into the tank. Always treat fish gently to reduce their stress levels and maintain their health, and never buy fish from a tank with obviously sick or dead specimens.