From FrugalReef

Marine Ich is caused by a parasite called Cryptocaryon irritans and manifests itself as white cysts on the skin of the fish about the size of a grain of sand. Ich can only infect fish, and can only survive in an aquarium without fish for up to 35 days, and less time the higher the temperature. Also, a single outbreak of ick can not last more than a year in an aquarium. That is, the ick in an aquarium will eventually die off even if fish are present to use as hosts. This is assumed to be because of cell aging.

[edit] Identification

Ich is characterized by white salt grain size flecks on the fish. The fish may scratch itself often by striking decorations with glancing blows. Heavily infested fish may show signs of stress such as not eating. Some fish, such as hippo tangs, are more susceptible than others.

[edit] Treatment

Only two treatments have been scientifically studied for the treatment of ich. Hyposalinity (Low specific gravity), and copper. Copper is also poisonous to fish, so between the two I prefer hyposalinity. The best case scenario is to move the fish to an empty bare bottom quarantine tank with a specific gravity of 1.009-1.010 and to do 50% water changes and complete cleanings each day for two weeks, followed by a slow specific gravity increase of about .001 per day until sg is normal. Observe for another 3-4 weeks. The tank may contain a simple smooth decoration for hiding such as a PVC pipe.

Bare bottom and smooth hiding places is preferred because the parasite falls off the fish and attempts to attach to substrate in order to divide, but does not attach well to smooth surfaces. Also, ich tends to detach at night and settle into the fishes "sleeping spot", so clean that pvc pipe thoroughly every day and make sure the fish has a stable day/night cycle so that he will reliably enter the pvc at night to facilitate removal of the parasite by cleaning.

Increasing temperature to the mid 80's will speed up the lifecycle of the parasite and improve the effectiveness of this treatment if the fish in question can tolerate it.

Most fish can tolerate reduced salinity without any problems, but sharks and rays are notable exceptions. Moving the fish from regular salinity to low salinity will not usually cause any stress but moving from low salinity to high will so take it slow when you adjust the salinity back up to normal.

[edit] See Also

• http://www.reefkeeping.com/issues/2003-08/sp/index.php
• http://www.wetwebmedia.com/ichartmar.htm
• http://www.petsforum.com/personal/trevor-jones/marineich.html