Soaking the food in garlic has helped me in the past. Those fish are pretty delicate and will more thank likely take a while before you can get rid of the ich. The ideal thing to do would be to setup a quarantine tank with medication. I wouldnt add any medication to the display. Ich without a host after a couple of weeks will die off. There are also some stages in the life cycle of ich where the medicine simply wont do anything, especially in the larvae stage and the earlier stages. If you dont want to use any medication, you can also try hyposalinity in a seperate tank