Ich is really variable in it's physical appearance and virulence - there are well researched papersin the scientific literature on low saliity reisistant ich, and comparisms of big/small spot ich and so on. Looks like you're lucky enough to have an infestation of very weak ich. Guess you can use UV, or if you're determined get everything out and stick them in something like a koi display vat for a few months with copper or whatever you like to use.
Point to bear in mind for untamed 12. Cryptocaryon populations were demonstrated to die out after I think about 22, 24 months if they were not exposed to any new genetinc material to crossbreed with due to genetic senescence. So if you've been suffering it for 18 months, and haven't added any new fishes, you're gettign close to having an ich free tank. It also means it's still worth qt'ing to make sure you don't get any new genetic material in, particularly one of the 'tank wipeout' flavours that seem to have been doing the rounds this year.