OK let's resolve the ammonia in QT problem once and for all. There are many ways to do this, so below is just my preferred method:
First thing you need is an Aquaclear HOB powerfilter. Which model? Well, that depends on your size QT. Typically, I use the AC50 on my 10-20 gal QTs, but bump it up to the AC70 for my 29gal. They also make an AC110 for larger QTs (55-75). However, you can always turn the flow down if needed ... so don't be afraid to get a bigger one than you think you'll actually need.
Why Aquaclear? Because they come with these really porous sponge/foam inserts (see pics at bottom), great for housing nitrifying bacteria which breaks down ammonia once you run water thru it. You can also buy replacement foam inserts for cheap (online).
How do I "seed" my foam insert with nitrifying bacteria? There are two ways. First is the way I do it ... it's the cheap way but also takes about a month. I place the foam (or multiples) in a high flow area of my DT’s sump (or you can put it behind your rocks) for at least one month prior to QT. This one month allows time for enough beneficial bacteria to transfer onto the sponge, so that it may be used as biological filtration once placed back in the power filter and used in QT. In actuality, I always just keep a foam or two going down in my sump, so I'm always ready for QT. Option #2 is to instantly seed your sponge with one of these bacteria in a bottle products: Bio-Spira, Seachem Stability, Dr Tim's Nitrifying Bacteria, etc. If you go with this option, you will want to slowly pour the bottle over the foam while it is inside the powerfilter chamber with just a little SW covering it. Let it sit for about an hour, before turning the powerfilter on, so that the bacteria can "settle" into their new home (the foam.) Also, it's best not to use copper (or any medication) for a few days to allow time for the bacteria to begin colonizing.
As mentioned previously, these foams are highly porous and capable of housing mass quantities of nitrifying bacteria to break down ammonia. They also do not absorb medications (such as copper) like LR does. I've never had any absorption or ammonia issues while using them. The only WCS I ever do in QT (using airline hose) is to siphon uneaten food/fish poop off the bottom (only because it bothers me.

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P.S. I never use the carbon bag/ceramic noodle thingys that come with the Aquaclear HOB powerfilter. Only the foam/sponge insert. If I need to run carbon in one of my QTs (which is rare), I only use Rox 0.8 is a media bag (or reactor) due to HLLE concerns.