A great set of articles from Advanced Aquarist...
http://www.advancedaquarist.com/2003/11/mini
http://www.advancedaquarist.com/2003/12/mini
http://www.advancedaquarist.com/2004/1/mini
http://www.advancedaquarist.com/2004/2/mini
A great review of the lifecycle of the ich.
Why the suggested lengths of treatment.
Scientific data to back up the claims.
Did you know there is a strain of ich resistent to hyposalinity.
Ich only feed on host for 3-7 days before falling off.
Then encyst on the substrate and reproduce to form 200 to 1000+ progeny.
Then only have 12 to 48hrs after they excyst to infect a new host.
He stresses that ich IS NOT present in all SW tanks. And can be eliminated and prevented with proper QT and treatment procedures.