Yeah you can, just get a couple of the ugliest pieces you have and use them. But, only if you do not use any copper treatment. I would assume the rock would absorb some and release it back into the water over time. They hyposalinity is what I use and have had excellent results.
If you use copper, use a sponge from the sump in a hob filter, after the qt period is over, throw out the sponge and place a new sponge in the sump for next time. Always have the sponge ready for that emergency situation.