Another good page is: http/www.cichlid-forum.com/articles/ich.php
Cool I'll have a read
After reading these articles, I am still unsure how to tell when to use the ich medication.
Immediately, and up the temp.
How does one know when the parasites reaches the thermont stage? I think it is pointless in using medication if these parasites are still on the fishes body.
One doesn't know and that's the point. There will be various parasites at various stages all the time. Whilst the parasite is visible on your fish, how many more are invisibly swimming about ready to find new hosts? Hence immediate medication. If I didn't have any meds I'd drop the temp further to slow down the multiplication, you've seen for yourself how quickly it spreads.
When I last checked 3 hours ago, all the tetras had ich on them and 2 of the 3 clown loaches had about 15 white spots spread on their tail, fin and body. I vacuumed the gravel, removed the carbon from the filter and did a 25% water change before adding my ich medication.
I hope I've done the right thing and can fight off the ich successfully this time. How long does it usually take for ich to go away? Is there anything I can do now apart from waiting? I shouldn't do any water changes should I?
You have done the right thing, it's a question of time now. You could cut down/switch off the lighting to reduce the stress the fish are under.
I'd expect it to be a good two weeks, at 82-84 degrees. I seem to recall the Tomonts hatch within 8 days (but I can't remember where I saw that so don't take it as gospel), so in theory 8 days from the last white spot dropping off a fish.
Continue with your water changes, but for any water you remove, medicate the replacement water proportionally.
I'm sure it's debatable whether to carbon filter out the meds or let them get slowly diluted by water changes, once you think it's treated. My line would be to leave it in in case I underestimated the time and some tomonts were still alive, and in a couple of weeks drop the temp again. That does mean that you don't really need to worry too much about when it's gone, just keep monitoring that there aren't any reappearing.