They will attach if they don't move, but the likelihood they will move if not glued is high. They probably ought to wobble about for a while until you are sure where they need to be, but after that, get some IC-glue and glue them into the rockwork. You can break off the rock they're glued to and glue them straight to the rock once you know definitively where they belong. And if you really need to you can break them loose again. IC-Glue doesn't hold forever.
You're starting with a pump and frags at the same time. Have you got your alk, cal and mg test kits? Start doing that, along with salinity and temperature, and keep a log with your readings. If anything goes wrong, you'll have a ready reference for what preceded it.