How many Discus do you need to move?
You can use 5 gal buckets half filled with tank water. Make sure you don't let any media from filters stay out of water to long.
You have no choice as you say so good luck with the transfer and sure all will go well.
Can't help with sick Discus without knowing more info... http://forum.simplydiscus.com/showth...lease-complete
...Ralph