Do a 20% water change and see what happens. Also, if you need to treat for any diseases, the rock will have to go. A proper qt
tank need to be bare bottom, with just some pvc
elbows for the fish to hide in.
Also if you need to treat with meds, the carbon would have to go. This will absorb any med you would put in.
If its cycled, thats great but keeping water parameters under control in a qt
tank is achieved by water changes, depending on the bioload. Or you can keep a small sponge in the sump of your main. If you need to set it up, just put the sponge it the qt
tank filter and voila, instant cycle.