It's almost a given fact that Clown loaches get ich, both after being shipped, and when acclimated to our tanks, no matter how slowly we do it. I had good luck treating with Maricide, I've heard Coppersafe and Aquarisol work as well.
MY original 6 gopt it twice before I finally rid them of it. THey stayed in an iso tank for at least 3 weeks after the last spot. When I moved them to their larger tank they never showed a spot, as by then they had gotten more used to my water and changing schedule.
Also the smaller the clown loaches are the more likely they will get ich. I picked up two bigger clowns (~6 inches), and they never developed ich, even when shifted between 3 different water parameters in one day ( they were returns to where I work, and I brtought them home for free. )
Link on ick treatemtns for Clown Loaches
http://www.loaches.com/copper.html
--Mia