When is it safe to add Discus?

[FairyDiscus]

I have an established tank and filter which is a year old. I have just changed to an external filter with all new filter media whilst keeping the other filter in the tank to help it mature. How long until it is safe to add Discus? I am keeping my other fish in there to help with the process and i plan on taking them out a day just before adding Discus.

[dishpanhands]

I wouldn't do it that way...I would start with a empty tank. Do a fishless cycle using clear ammonia. this way no chance of spreading a bad thing to your new discus..You do a search on this forum for "fishless cycle" they will tell you how to do it...
HTH