yes no sand or rock needed in QT, thats a lot of life to add to an un cycled tank. At least your gonna save em
thats all that matters. You will find keeping a SW tank is much more complicated than a FW one. I did too when I first started lol. This forum is the best, there are always so many ppl with great ideas and experiences to help you out.
I would do a 2g or so water change every few days in the QT to export unwanted nutrients, and pick up some seaweed... I believe its like kori seaweed or something like that... without rocks and such to pick on you will want to put a piece in every week or so to keep the hermits and the urchins fed.
your cycle should be over in a few weeks. also you will want some flow in the QT, a regular carbon filter should be plenty. Good luck