DONT USE SALT ON THE CLOWN LOACH!!!!!!!!!!!!!!!!!! The salt will harm it! For the tetra and the other fish(if any get ich after this)use a normal ich treatment. For the clow loach use an ich treatment designed for scaleless fish, and don't let it come into contact with the normal ich preventative...
Turn the temature up to about 82 degrees this will speed the life cycle of the ich then put in a ich treatment. The only time the treatment will have a effect is when the ich lifecycle are at the freefloating stage. DON'T USE SALT. raise the tempature up slowly over two hours.