Hi Beth,
It have no sign of ICH for three weeks, if I wait for another 4 weeks, am I able to get more fish (5-6)?
You don't have to wait another 4 weeks. Ick has a 3-4 week reproductive cycle, after which it must find a host within 24-48 hours, or it will die. I would wait another two weeks to be safe. Please don't add 5-6 fish at one time. No more than one or two at a time, so the system can adjust to the new additions.
I hate to disagree with the powers that be, but I have to disagree with daily water changes. This will
not rid your tank of ick. When ick is in the reproductive cycle (tomont stage), it's attached to the substrate in your tank, so changing water accomplishes nothing. Ick will remain attached to the substrate for 3-4 weeks as it multiplies. Even if it
has moved into the water column in search of a host fish, the chances of getting all of it are very slim, at best. You're just wasting salt...