Reading these threads, is like a recipe for disaster.
And adding chemicals, is like adding salt to the brew.

Discus, are very specialised, some people have no trouble with them and some
people have no end of trouble with them.

You say you have a tank up and working, cycled, acclimatised, or whatever.
What's wrong with talking half the water out of that tank and sticking it
in the new tank, then over a period of time add more water , until the tank
is full.. As for talking dirty water from a filter, and adding it to a
clean system,, Your Dreaming...

One rule, If you don,t have, or can't acquire natural "Sof****er" don,t
bother with Discus. Once you start adding chemicals to water, you can NEVER
remove it.

And if the Discus, loose colour, or go dark, your going to loose them,
there going to die, your wasting your money. simply because your conditions
are wrong for Discus
bassett