If your tank has no fish for 6+ weeks the ich will die because of no host. Now if you add a new fish that has ich (takes a while before it can be seen on the fish) then you have ich again. You can only get ich if you introduce it to the tank. If the tank is empty for 6+ weeks the ich will die.

Copper is a great tool and one of the few that actually work with ich. We recommend that the first treatment you do the recommended dose, then the next day you do half the daily dose 12 hours apart.

If you have no fish in your tank, why are you quarantining in the 29 gallon? Do you have corals and inverts in the main tank?

(1) A 29 gallon tank can house about 15 inches of fish. Sounds like enough room.

(2) QT doesn't have to be simple, but the copper will kill a lot of inverts. Yes, use the existing water from your display tank. I would recommend a piece of live rock or two for good hiding places. You can always put them back in your display after you are done and given enough time they will become 'live' again. Use a dirty filter pad from your existing tank to set up the QT. No...just use everything from your display tank so that the cycle is little.

(3) as often as you like. The copper leaves the system pretty quick so it is good to test to see what levels you have it at and keep it at.

(4)double check that the cowfish can tolerate copper. I don't think so...but can't remember why I think that.